1 ing Mobile, Anti-Aircraft, and Trench Materiel, information and guidance of all students of the Ordnance training The contents schools, and other similar educational organizations.
'

of Artillery, Includis published for the

should not be republished without authority of the Chief of Ordnance; War Department, Washington, D. C.

BY ORDER OF THE SECRETARY OF WAR.

PEYTON
OFFICIAL
P. C.
:

C.

MARCH,

General, Chief of Staff.

HARRIS,
The Adjutant General.
(3)

432322

PREFACE.
in this book is compiled for use in the Ordnance training and other educational organizations where a short, yet comprehensive, survey of the existing calibers and types of guns and carOn this riages now in use by the United States Army is desired. the descriptions and drawings have been made simple and basis, technicalities have been reduced to a minimum, bringing out the differences and similarities of the various types of artillery materiel. This publication has been prepared in the mobile gun carriage secThe general discussion on the design tion of the Artillery Division. and characteristics of mobile artillery is intended for the instruction of student officers and enlisted specialists schools. The first edition of this book is to be distributed to various educational institutions for a trial use in their classes and the results of

The data

schools

.

this trial should be productive of many constructive criticisms so that the second edition will more fully meet the varied needs of the

The intention is to revise this book schools and training units. therefore suggestions and criticisms are cordially periodically, Communications should be addressed to the Chief of Artilinvited.
lery Division, Office of the Chief of Ordnance, Washington, D. C.
Murray H. Resni
Coff.

LIST OF CONTENTS.
Page.

List of illustrations

.'

7

Table

of equivalents
'.

14
15

Brief history of guns and artillery materiel
Artillery, classes of

21
21

Mobile artillery, types of Guns, their functions and construction, including breech mechanisms Mounts for mobile artillery
Recoil brakes and methods of counterrecoil

Hydro-spring recoil system Hydro-pneumatic recoil system with floating piston Hydro-pneumatic recoil system with fluid in direct compact with the Counterrecoil mechanism (hydro-pneumatic, central buffing)

35 36

Aiming devices:
Elevating systems
40
41

Panoramic sight Gunner's quadrant

42
:

Accompanying vehicles

Tractors hauling artillery 75 mm. gun carriage, mounted on trailer

46 ^47
49 50 51 53
left in

37-millimeter

gun materiel, model of 1916: Rear view of carriage in battery position Carriage and ammunition cart, limbered Left side view of tripod mount in battery position
Tripod mount in firing position Gun disassembled on the march (wheels and axles

:

the rear) Gun and personnel on the march (ammunition cart left in the rear) 37-millimeter (1-pounder) gun carriage (Bethlehem):

Pack outfit on mule back Rear view of carriage in battery Detailed view of gun Side view of carriage in battery 75-miUimeter gun materiel, model of
Right side elevation of carriage Front view of carriage Plan view of carriage

63

64
1916:

66

66
67 68

Rear view of carriage Left side view of carriage Breech mechanism
Longitudinal section of recoil and counterrecoil mechanism

155-millimeter howitzer materiel, model of 1917 (Schneider): Right side view of carriage in traveling position
Carriage in battery position (rear view) Front view of carriage in battery position Side view of carraige en route

208 209 209 210 212
. . . .

155-millimeter howitzer materiel, model of 1918 (Schneider):

Traveling position of carriage and limber Assembled views of traveling position Detail view of howitzer Breech mechanism Firing mechanism Recoil and counterrecoil mechanism Longitudinal section of howitzer and carriage

A BRIEF HISTORY OF GUNS AND ARTILLERY
MATERIEL.
In taking up the study of guns, the student should
of their history, the development of reason for the various changes in

know something guns and gun carriages, and the ordnance materiel which have

taken place from time to time. The first use of guns or cannon as a medium for hurling projectiles by means of gunpowder is buried in obscurity; we have knowledge
of Chinese using a form of gunpowder, not, however, for military purposes, but for pyrotechnics, at a period long before the Caucasians.

From
kill at

the earliest times

man

has

felt the

want

of

arms that would

a distance, and the ingenuity of the talented has successively been taxed to produce such weapons. The readiest means at first was the throwing of stones or spears with the hand; but the effect of the missile proved so often insufficient that at once a desire arose to The sling assist the muscles by the aid of some mechanical force. Its invenmissiles. was probably the first weapon used for hurling
tion
is

attributed to the Phoenicians or the inhabitants of the Balearic

who were extremely expert in its manipulation. The sling was used for many centuries as a military weapon, and its last appearance
Isles,

was at the Huguenot War of 1572. The bow was probably invented about the same time as the sling, and for many centuries was considered the most effective offensive weapon in warfare. Great skill was attained by the ancients in its use, and many accounts are to be found relative to the extraordinary The force and precision with which an arrow might be projected. has always been more essentially the universal weapon, the long-bow cross-bow being a comparatively modern invention, and its use confined almost entirely to Europe. The cross-bow was greatly used for sporting as well as military purposes and it must have been
;

employed in his notable feat. The Genoese and Gascons were the most famous cross-bow men in the armies of Europe. The cross-bow of the fourteenth and fifteenth Some centuries were sometimes made with sights affixed to them. a back sight having three or more peepholes, specimens possessed one over the other, which were evidently intended as guides for
a cross-bow that William Tell
elevation.

The invention of gunpowder is possible to trace back to many Most writers upon this subject centuries prior to the Christian era. seem agreed that it was known to the Chinese and Indians, but the
18322820
2
(15)

16
descriptions given are so vague that it is difficult to make the various accounts coincide. The earliest mention we have of gun-

Gentoo Laws, where it is mentioned as applied to This particular code is believed to have been coeval with the time of Moses. Gunpowder has been known in India and China far beyond all periods of investigation. There are many ancient Indian and " heaven's thunder," Chinese words signifying weapons of fire, " devouring fire," "ball containing terrestrial fire," and such like

powder

is

in the

firearms.

expressions.

The ancient Indians made great use of explosives, including gunpowder, in pyrotechnical displays. The introduction of powder into Europe took place early in the Christian era; some believe it was
brought by the Moors into Spain and others that it came through Both may be correct, but certain it the Greeks at Constantinople. is that it, or a substance closely akin to it, was used at the siege of Constantinople in A. D. 668.

The Arabs,
said to

or Saracens, are have used it in A. D.
earliest
is

690, at the siege of Mecca.

The

mention

of

guns we have

that Seville

ARTILLERY OF THE SIXTEENTH CENTURY.

was defended in 1247 by cannon throwing stones Mibela in Spain was also defended by a machine resembling can;

non,

when

besieged in 1259;

in 1273, Abou Yousof made use of cannon throwing stone balls at the siege of Sidgilmessa; and in 1308, Ferdinand IV of Castile, at the siege of Gibraltar, employed guns (or Marquinas de Truenas); and in 1311,

Ismail attacked Bazas, a town of Granada, with machines throwing
balls of fire with a noise resembling thunder. These seem to confirm the opinion that the use of cannon and powder was known to the
4

Arabs or Moors and introduced by them into Spain, from whence it spread over Europe. In the chronicle of the town of Ghent for 1313 it is stated that the town was possessed of a small cannon; and in the records of the Florentine Republic mention is made in the year 1325 of two officers being ordered to manufacture cannon and iron bullets for the defense of the castles and villages belonging to the Republic. The first German cannon belonged to the town of Amberg, and bears the date of 1301. The English appear to have imported them from

who used them

Flanders, for King Edward III in 1327 employed some Hainaulters in his war with the Scotch. In 1331 cannon were

used by the King of Granada against Alicante, in 1339 at the siege of

17
Puy-Guillem, and in the same year at the siege of Cambray by Edward III, in 1340 by Lequesnoy before Mirepoix, in 1345 before Monsegur, and in 1346 at Crecy; we have many instances of cannon being used in the second half of the fourteenth century. About 1350 the North German knights had iron guns, and a little later the Free Hanse Towns armed themselves in the same way. In the year
1356 appear large amounts in the accounts of the town of Nuremberg having been spent in purchasing cannon and guns; and in 1365 Duke Albert of Brandenberg defended Einbeck very effectually
as

"with

fire

boxes."

records show that the Huns used artillery at the siege of The materiel was, of course, very crude and Cividale, Italy, in 1331. its effectiveness at that time depended largely upon the smoke and

The

first

noise produced. The barrels, or cannons, in those days were constructed of wood, wrapped with wire or iron bands, and the proThese guns were not mobile guns in any jectiles were of stone.
sense; they were transported with the utmost difficulty, subject to capture by sudden raids of the enemy.

and were

British were the first to actually bring the guns out into the field of warfare. They appeared at the Battle of Crecy in 1346, much to the dismay of the enemy. They shot anything that would

The

go into the barrels of the guns, even bundles of arrows. The ordnance department of Edward III consisted of 340 men, with but 12 artillerymen, showing that at that time not much attention was paid In 1415 the to what is now an indispensable arm of the service. numbers had increased to 25 " master-gunners " and 50 "servitourgunners." The gunner was the gun captain and had general charge of the gun and stores. In action he laid the piece and did the actual
firing.

The

bombardes, probably derived from "a bombo et ardore" on account of the The French called great noise which the firing of them occasioned.

different

early cannon of Europe were known In Italy they were countries.

by various names

in the

known

as

them "quenon" or "cannon," the Germans "buchsen" or "boxes," and the Netherlanders "voghdeer" or " veugliares." Besides these
terms there were

many

was not
were

until the

classified

commencement of the and named according to

others applied to the various models, but it fifteenth century that cannon
their size.

Cannon was not

adopted or manufactured in France until 1338, and even for many years afterwards the French looked upon those nations who used

cannon were made of wrought not have of cast cannon being in 1378, when a founder named Aran, at Augsberg, in Germany, cast 30 of a metal composed of copper and tin. In 1413 Mahomed II, at the The bore siege of Constantinople, had an enormous cast cannon.

them as barbarians. The early cast metal, the first account we

18

19
said to have boon 48 inches in diameter and the stone bullet to have weighed 600 pounds. The greatest example of artillery in the fifteenth century was at
is

of

the siege of Constantinople in 1453, by the Turks. They used a type mortar that hurled huge stones, some weighing 700 pounds. Some of these guns survived to engage the British in 1807; the

majority of artillery at that date was for siege work. Barons who had quarrels with their neighbors would rent ordnance and go out and batter down their castles. In the Italian wars waged by Charles VIII of France, artillery played a conspicuous part. However, they lacked the necessary mobility and, consequently, were captured and recaptured several times in a single engagement. At that, artillery had done some excellent work before small arms had attained any prominence. Although field artillery was introduced in the Hussite Wars, 1419 to 1424, it was not until the Thirty- Years War that they really displayed a mobile nature. The French had invented the limber, and the connection between it and the gun trail was made with a rope. The first gun that was moved by horsepower was mounted on an oblong frame, the gunner sitting directly behind the piece. The forepart of the oblong was mounted on two wheels and the rear end was supported by the horse which was inside of the oblong frame. The majority of the guns were 4-pounders, for as yet no way had been devised for
the proper transportation of the heavier guns. About the middle of the eighteenth century, guns were either 24, 12, 6, or 3 pounders; the units were divided into brigades of 4, 5, and
6 guns respectively,
units.

Each

each of

and began to be separated into heavy and light gun was drawn by four horses with a cannoneer on The ammunition carried was 100 rounds of the lead horses.
field

solid shot.

The howitzer, needed
in

for its high angle of

fire,

put in

its

appearance

Horse artillery 1785, being introduced by the French Army. appeared in the French Army in 1791. In 1800 the horses were

paired off with a driver on each near horse as is done to-day. In 1808, at Vimera, the first shrapnel came into use. It was known as case

shot and the type used

by Napoleon had

a fuze that could be used for

Napoleon also introduced the idea of massing Between 1860 and 1870 rifling appeared; artillery along a long front. this caused sighting to be given greater consideration, as a rifled gun shoots very accurately. During our Civil War the smoothbore was generally used, although rifled guns had made their appearance toward the close of the conflict. Direct laying was the only method
different ranges. of fire

two

employed

at

this time.

With the breechblock came the

This called for a recoil mechanism, in order that quick-firing gun. the lay of the piece would not be seriously disturbed as a result of

20
of smoke produced with the powder then from the gunner and, unless quite a wind was blowing, the shooting was slow, but with the development of smokeless powder in the late nineties, this latter fault was done away with and rapid firing was possible. The first shields were put on the guns about this time also, protecting the gun personnel and making the
firing.

The vast amount

in use hid the target

piece

struggle in Europe has brought about conditions and problems which heretofore have never existed in warfare. To meet these, sweeping changes have been made in almost every arm
of the service, but probably the greatest and most radical change has been the motorization of the artillery. Heretofore successful advances by the troops were limited to comparatively short distances, due to the impossibility of advancing artillery, ammunition, and supplies over grounds which are often muddy, full of shell holes, and otherwise difficult to maneuver with enough rapidity to keep up with the advancing infantry troops.

more difficult The recent great

to put out of commission.

The problem of transporting army equipment in the field led to the introduction of tractors and motor trucks. The development of the caterpillar tractor used for hauling field
artillery, which is able to negotiate almost any kind of terrain on the battle field, led to the question of the possibility of mounting guns directly on a self-propelled vehicle equipped with caterpillar treads.

Early in 1918, an 8-inch howitzer was mounted on a self-propelled to 45 caterpillar and was fired at angles of elevation varying from with very satisfactory results. This experimental caterpillar was tested, and it was found to be practical, easy to maneuver, and able As a result of this to withstand the firing strain of the howitzer.
types of experimental self-propelled caterpillar units are being built with armaments varying from 75-millimeter guns to 240-millimeter howitzers.
test, several

ARTILLERY.
Artillery has

come

to

mean

all

firearms not carried or used
is

by hand,

excepting machine guns.

Artillery

divided into two general classic

fications: Artillery of position and mobile artillery. Artillery of position is that which is permanently
fications.

mounted

in forti-

Mobile artillery consists of two classes: First, the artillery designed accompany an army in the field; second, railway artillery, which The first type only is disrequires tracks for its transportation. cussed in this book.
to

MOBILE ARTILLERY.
In designing any gun intended for use in the field, there are two important requirements power and mobility. Granting that a general type of gun has been decided upon, it is evident that any increase in either of these two factors is at the expense of the other. It is necessary to balance the two, keeping in mind the specific purpose of the gun under consideration. We thus find it necessary to have several distinct classes of guns, ranging from the very powerful and almost immobile, to the very mobile and comparatively weak. The
general classification is heavy field, light field, mountain guns or pack howitzers, trench mortars, and infantry accompanying guns and howitzers. Besides this classification, based upon power, there is a second,

based upon the shape of the trajectory. For the attack of targets that can be reached by it, flat trajectory fire is prefesred on account of its power and accuracy. Cases frequently arise, however, where such fire is useless, either the gun or its target being so concealed and sheltered by intrenchments or the condition of the terrain that higher

become necessary. To provide for both cases, there are two or three types weapon the long gun for flat trajectory, the shorter howitzer
angles of departure and fall

of for

curved trajectory, and sometimes the still shorter mortar for highWe thus subdivide our original classes and distinguish, angle fire. for example, the light field howitzer, the heavy field gun, etc. Evithe number of separate calibers that might be adopted to dently

make up
of

tant to reduce this

a complete series of types is very large. But it is impornumber to a minimum, both from considerations

economy and also to avoid complication in ammunition supplies. Guns were ordinarily intended for attack of targets that can be reached by direct fire; that is, by fire at angles of elevation not exceed(21)

22
ing about 15.
direct fire
fire

For the attack of targets that are protected against and for use in positions that are so sheltered that direct

can not be utilized, curved fire that is, fire at elevations exceedis necessary. There is, therefore, provided the howitzer, a ing 15 short gun designed to fire at comparatively large angles of elevation. Field guns are now designed which permit fire at elevations as high or higher than is permitted by the howitzers. This is partic-

and those designed for use against This development is an improvement in the effectiveness of the field gun, -but it will not eliminate the use of howitzers of equal mobility, as the latter use projectiles of much greater weight than that of same caliber gun materiel.
ularly true of anti-aircraft guns

entrenched positions.

The original American plan of field artillery design provided for each caliber of gun a howitzer of equal degree of mobility. In furtherance of this idea and to reduce to a minimum the number of calibers of mobile artillery and thus simplify as far as possible the supply of ammunition, the calibers of the guns and howitzers were so selected that while both guns and howitzers fulfilled the requirements as to weight and power for each degree of mobility the caliber of each was the same as that of the gun of the next lower degree of That is, the howitzer corresponding in mobility to one of mobility. the guns is of the same caliber as the next heaviest gun. The recent developments in American artillery, as well as the introduction of
artillery of foreign design into the this principle.

American

service,

have sustained

Under ordinary conditions the 3-inch field gun with its weight of about 3,900 pounds behind a six-horse team, is about as powerful a gun as can follow an army in motion. For this reason a gun of approximately this caliber has been adopted by most nations as the
principal field gun. The artillery of all military powers now comprises what are known " " " " as rapid-fire or quick-firing guns. This designation is too firmly established to be changed, although it can not be considered as accurately descriptive since rapidity of fire is characteristic of nearly all modern types. The real distinguishing mark of a rapid-fire gun is that

carriage does not move materially in firing; instead, the gun recoils on the carriage and is returned to the firing position by springs or their equivalent. There are a number of other features, some of which are found in all rapid-fire models; but these are of secondary significance and either old ideas which could not be worked out
its

practically before the development of the gun-recoil carriage or else improvements developed since in the effort to get the best results out
of
it.

For example,

it is

useless to attach shields to a rigid carriage,

for, since

the cannoneers have to stand clear to avoid the recoil, they can not take advantage of them. Mechanism for traversing the

23
piece on its carriage is unnecessary with the rigid system, but becomes necessary as soon as we adopt a carriage that remains more or
less firmly

anchored to the ground.

Fixed ammunition and instru-

ments

for indirect laying are not essentially a part of either a rigid or a gun-recoil system; they are sometimes used with the former and

full

occasionally, but rarely, omitted from the latter; but they value only in rapid-fire material.

have

their

artillery is divided into the following classes: Divisional artillery, such as the 3-inch, 75 millimeter guns, and 155 millimeter howitzers.
(a)

Our mobile

such as the 4.7-inch and 155 millimeter guns. (c) Army artillery, such as the 8-inch and 240 millimeter. Any caliber may, if required, be assigned to army artillery corps. U (d) Mountain or pack materiel transported on the backs of mules.
(6)

Corps

artillery,

For mountain service the system composed

of

gun and carriage must

be capable of rapid dismantling into parts, none of which forms too heavy a load for a pack mule. The weight of the load including the saddle and equipment should not exceed 350 pounds. The mountain gun in our service is the 2.95-inch.
(e)

(f)

Infantry accompanying guns, such as 37 millimeter. Trench mortars.

GUNS.
THEIR FUNCTIONS AND CONSTRUCTION.
U

A

gun

is

a machine

by which the

force of expanding gas

is

used

for the

The

purpose of propelling a projectile in a definite direction." gun consists of a metal tube, closed at one end, of sufficient

strength to resist the pressure of the expanding gases, in which is placed a projectile designed to move through the tube. The force

expanding gases acting on the base of the projectile causes on its flight in a definite direction. When the charge is the explosion or rapid combustion of the powder gives rise ignited, by its decomposition to a large amount of gas, which tends to expand, and to occupy a space greater than that in which the powder was
of the
it

to start

originally contained; consequently,
tions,

it

exerts a pressure in

all

direc-

and the energy developed is utilized in forcing the projectile from the tube. The major portion of the energy is distributed as
follows
(a)
:

Energy of translation of the projectile. (&) Energy of rotation of the projectile. (c) Energy of translation, in recoil, of the gun. (d) Energy of translation of the unburnt charge and gases. (e) Energy consumed in overcoming the passive resistance of the This resistance arises from the friction of the projectile projectile. against the walls of the bore, and of the rotating band against the In the first stages it also arises from the driving edges of the lands. cutting of grooves in the rotating band by the lands.

The balance of the energy is expended by being lost as heat to the gun and that which remains in the gas as sensible or latent heat
be readily understood that during the travel of the prothrough the bore of the gun, from the instant of ignition of the charge until it has left the muzzle, tremendous rending stresses are set up in the tube. In the earlier days of ordnance construction, these stresses were met by sheer weight of metal; but as the weight of projectiles increased, with consequent increase in powder charges, this weight of metal became so great as to impede the desired mobility of the material. Consequently, forgings of refined and alloyed steels took the place of the castings or forgings of iron or simple steels. As explosives increased in power, the plain tube, even though built
It

may

jectile

of alloyed steels,
sures,

became incapable

of containing the

chamber

pres-

even though of excessive weight. This problem was finally met through the construction of built-up and wire-wrapped guns.
(24)

25

A gun is subjected to two fundamental stresses a circumferential tension tending to split the gun open longitudinally, and a longitudinal tension tending to pull the gun apart lengthwise. The longitudinal strength of a gun is usually greatly in excess of any requirements.
It

easy to demonstrate that any homogeneous gun, i. e., a gun made and not built up, soon reaches the limit of thickness beyond which additional thickness is practically useless in giving strength to resist circumferential stress. This is due to the fact that the stress on the metal near the bore is far higher than that on the
is

of solid material

outer portion and soon reaches its maximum resistance, which addiThe gun can, tional thickness of metal does not materially increase. however, be arranged to withstand a considerably higher piessure

by building
ers of the
first

it up on the principle of initial tensions. The inner laymetal are thereby compressed so that the gas pressure has to reverse this compression and then extend the metal. The

barrel (or tube) supported by the contraction of the outer hoops then be able to endure a gas pressure which can be expressed as proportional to the initial compression plus the extension, whereas in the old type of solid gun it was proportional to the extension only. In the built-up system, the outer jackets are shrunk one over the other so that the inner tube is placed in compression and the outer ones in tension. In place of one or more of the jackets, a thin wire or ribbon of steel is sometimes wound around the tube and has exactly the same effect as shrinking thin jackets one over the other. This type is known as the wire-wound gun. Guns may be composed of two, three, or more cylinders; though in

gun
will

All practice guns are hardly ever built of more than four cylinders. small howitzers or mortars, are of the built-up or Army guns, except

wire-wrapped type.
the bore.
Rifling consists of a number of helical grooves cut in the surface of The soft metal of the rotating band of the projectile is

forced into these grooves and causes the projectile to take up the motion of rotation as it passes through the bore. Rotation of the projectile around its longer axis is necessary for stability in flight. By twist of rifling is meant the inclination of one
of the grooves to the element of the bore at

any point.
is

Rifling

is

of

two kinds: (a) Uniform
out the bore.

twist, or that in

which the twist

constant through-

(6) Increasing twist, or that in which the twist increases from the breech toward the muzzle end of the bore.

The

twist of rifling

of bore in

which

it

is usually expressed in number of calibers length makes one complete turn; this is called the twist

in calibers.

The

twist actually required at the muzzle to maintain

26
the stability of the projectile in flight varies with the kind of proand with the muzzle velocity.

uniform twist is used, the driving force on the rotating band be a maximum when the pressure in the gun is at maximum, or near the origin of rifling. The increasing twist serves to reduce the maximum driving force on the band, thus lessening the danger of stripping it with resultant loss of rotation of the projectile. This is its principal advantage over the uniform twist, though it also reduces
will

jectile If a

slightly the maximum pressure in the gun. vantage of increasing t wist is the continued

principal disadchange of form neces-

The

sary in the grooves pressed in the rotating band as the projectile passes through the bore. This results in increased friction and a higher value for the passive resistance than with a uniform twist. If the twist increases from zero at the breech, uniformly to the muzA zle, the rate of change in the tangent to the groove is constant. twist in this form would offer less resistance than the uniform twist to the initial rotation of the projectile. But to still further diminish this resistance, a twist that is at first less rapid than the uniformly increasing twist and later more rapid has been adopted for some
rifled guns.

ism,

The breech mechanism comprises the breech block, the firing mechanand the mechanism for the insertion and withdrawal of the block. There are two general methods of closing the breech. In the first method the block is inserted from the rear. The block is provided

with screw threads on its outer surface which engage in corresponding threads in the breech of the gun. In order to facilitate insertion and withdrawal of the block, the threads on the block and breech are interrupted. The surface of the block is divided into an even

number

of sectors

and the threads

of the alternate sectors are cut

a vay. Similarly, the threads in the breech are cut away from those sectors opposite the threaded sectors on the block. The block may then be rapidly inserted nearly to its seat in the gun, and when turned

through a comparatively small arc, say one-eighth or one-twelfth of a circle, depending upan the number of sectors into which the block is divided, the threads on the block and in the breech are fully engaged and the block is locked. In the second method, a wedge-shaped block is seated in a slot cut in the breech of the gun at right angles to the bore and slides in the
slot to close or

open the breech. Variations of these two methods will be noted in the detailed

descriptions of the guns which follow: The most notable variation from the above two types is the Nordenfeld type of breech mechanism, a rotating block construction

found on the French 37-millimeter and 75-millimeter, described more fully and illustrated in the description of these guns.

27

The breechblock

is

usually supported in the jacket of the

gun or

The seat in the jacket in a breech ring screwed into the jacket. of greater diameter than could be provided in the tube, the being
bearing surface of the screw threads on the block is increased and and the length of the block may be diminished. The slotted screw breechblock is used to a great extent in oui Its advantages are uniform distribution in the gun of the service.
longitudinal stress produced by the powder pressure and lightness permitted in the construction of the breech end of the gun. In the model of 1917, 3-inch anti-aircraft gun, however, and in the Ameri-

can 75-millimeter gun, the sliding block operating vertically has been adopted for the reason that it permits of simpler mechanism for semiautomatic operations. Howitzers differ only slightly from guns in their construction.

They

A

and insomuch as the chamber pressures the necessity for the long jacket is eliminated. shorter jacket, extending only a part of the length of the tube, shrunk on in the same manner, is generally used.
are shorter in length
differ materially

Interior/ ballistics treats of the motion of the projectile while still in the bore of the gun. It includes the study of the mode of combustion of the powder, the pressure developed, and the velocity of the

projectile along the bore of the gun. By means of the formulas developed, a study of interior ballistics has made it possible to design the granulation of the powder for a

given gun so as to obtain the highest possible muzzle velocity with a given weight of projectile, while keeping the pressure along the bore within the limits imposed by the strength of the walls of the gun, and the weight of the charge low enough for convenient loading. After the calculation of curves of velocity and pressure are made,
the walls of the

gun

are calculated to withstand the expected pres-

sure at each point from breech to muzzle.

MOUNTS FOR MOBILE ARTILLERY.
A modern gun carriage is expected to stand steady on firing, so that
it requires no running up, and in the second place maintains the direction of the gun so that only a slight correction in elevation and direction is required after each round. The caris maintained in position by the spade, which sinks into the riage ground, and by the friction of the wheels upon the ground. If the force of the recoiling gun were communicated directly to the anchored carriage the effect would be to make it jump violently, which would not only disturb the lay, but would prevent the cannoneers from maintaining their position. The hydraulic recoil brake is therefore

in the first place

it

interposed between gun and carriage. If the gun were rigidly attached to the carriage the latter would be forced back a short distance at each. round, and the wjiole of the Inrecoil energy would have to be absorbed in that short motion.

stead of this, the gun alone is allowed to recoil several feet and although the recoil energy is in this case greater than it would be if gun and
carriage recoiled together, yet it is so gradually communicated to the carriage that instead of a violent jerk we have a steady, uniform
pull, the

only effect of which is to slightly compress the earth behind In a well-designed carriage the amount of this pull is less than that required to lift the wheels off the ground by always rotating the carriage about the spade. The only motion of the carriage which takes place is that due to the elastic bending and rebound of its parts under the cross strain set up in discharge. These strains are inevitable since the direction of recoil can not be always exactly in the line of the resistance of the earth behind the spade. This movement of the axis is known as jump and must be determined by experiment for the individual
the spade.
piece in its particular mounting.

The principal parts of the typical gun carriage are the cradle; a device for mounting the cradle called in the different models a The gun
rocker, pintle yoke, or top carriage; the trail; the wheels and axle. slides in recoil on the upper surface of the cradle and the

the cradle contains the recoil controlling parts. In the design of the carriage the constructional difficulty lies not so much in preventing the carriage from recoiling, but in preventing

The

the wheels from rising off the ground on the shock of discharge. force of the recoil of the gun, acting in the line of motion of the center of gravity of the recoiling parts, tends to turn the carriage
(28)

29
over backwards about the point of the trail or center of the spade. This force is resisted by the weight of the gun and carriage, which tends to keep the wheels on the ground. The leverage with which the overturning force acts varies with the distance of its line of action above the center of the spade; the leverage with which the restraining force acts varies with the horizontal distance of the center of gravity
of the spade. It follows that the steadiness of the carriage for a given energy may be promoted by four factors.
of the
(a)

gun and carriage from the center

muzzle

Increasing the weight of the gun and recoiling parts. This reduces the recoil energy. This reduces the (b) Increasing the length of recoil allowed.

overturning pull. (c) Keeping the gun as low as possible, either by reducing the height of the wheels or by cranking the axle downwards. This reduces the leverage of the overturning force. This increases the lever(d) Increasing the length of the trail.
age of the steadying force. The well-designed gun carriage is one that combines these factors in a practical way, so as to give the greatest possible steadiness to the carriage, at the same time keeping within the limits of weight

imposed by the necessity of mobility.
carriages are so constructed as to permit movement of the in either a vertical or horizontal plane. These motions may piece be simultaneous if so desired, and by a proper combination of the

Gun

gun may be aligned in any desired direcmotion of its mount. The two kinds of motion are designated as follows: Rotation of the piece about a vertical axis, its inclination with the horizontal remaining unchanged,
of a

two motions, the axis

tion within the limits of

is

traversing "; movement of the piece in a vertical plane, the horizontal projection of the axis of its bore remaining unchanged,
called

"

is

mechanisms for giving the pieces controlled motion in both azimuth and elevation. Two accurately of elevating mechanisms are in common use. The first is the types
This gives a considerable length of screw for a telescopic screw. short assembled length and gives a rapidity of action (since the movement of the inner screw is equal to the sum of the pitches of the outer and inner screw for each turn of the pinion), combined

Gun

called "elevating." carriages are provided with

with the nicety of adjustment of a single screw of fine pitch. In the second type 'the motion is communicated to rockers, attached to the bottom of the cradle, through the engagement of worms or pinions, with teeth cut on the circumference of the rockers.

30
This method
It allows for a
is in use on all howitzers, and a great many guns. very high angle of elevation, and when fitted with a

quick-loading gear, allows for the rapid placing of the piece in loading position after firing. Movement of the gun in azimuth is accomplished in several ways;

one is to pivot the cradle of the gun in a saddle which itself pivots on a horizontal transom of the trail. Another is to mount the gun and elevating gear on some form of top carriage, and pivot this top carriage over the axle. Still another is to traverse the whole This is a method used piece along the axle, pivoting on the spade. by the French in some of their designs. It has the disadvantage of
only allowing for a small angle of traverse. The above principles of design are, of course, modified considerably in the case of semipermanent mounts which fire from platforms and
for anti-aircraft

guns which have special mountings suited to their

special use.

RECOIL.
RECOIL BRAKES AND METHODS OF COUNTERRECOIL.

The stresses to which a gun carriage is subjected are due to the Gun carriages action of the expanding powder gases on the piece. are constructed either to hold the piece without recoil or to limit the In the first case, the maxirecoil to a certain convenient length.

mum

is readily deduced from the maximum In the second case it becomes necessary to determine all the circumstances of recoil in order that the force acting at each instant may be known and the parts of the carriage designed to withstand this force and to absorb the recoil in the

stress

on the carriage

pressure in the gun.

desired length. Assume the gun to be so

mounted that

it

may

recoil horizontally

and without

resistance.

On

explosion of the charge, the parts of

the system acted upon by the powder gases are the gun, the projectile, and the powder charge itself; the latter including at any instant both the unburned and the gaseous portion. While the prois in the bore, if we neglect the resistance of the air, none of jectile

The center

the energy of the powder gases is expended outside the system. of gravity of the system is therefore fixed, and the sum of the quantities of motion in the different parts is zero. The moveof the

ment

will be principally in the direction of the formula, the weight of the gun, projectile, and projectile. charge being known, the complete relations between the velocity,

powder gases

By

and length of free recoil may be established. Thus far we have neglected all resistances and have considered the movement of the gun in recoil as unopposed. However, when the gun is mounted on a carriage the recoil brakes, of whatever character, begin to .act as soon as recoil begins, and consequently
time,

unopposed.
little

the velocity of recoil is less at each instant of travel than when It is evident that the higher the resistance offered by

the recoil brakes, the shorter will be the total length of recoil. consideration will show that if the total resistance to recoil

A
is

constant throughout the recoil, its value will be less than the maximum value of a variable total resistance which will stop the gun in the same length of recoil. For a given length of recoil; the constant resistance will therefore produce less strain in the carriage,

made

and for

this

reason
3

is

usually adopted, except where stability can be
(31)

increased

by using

a variable pull.

18322820

32

The recoil system of a gun carriage consists of a recoil brake for controlling the recoil and limiting its length, a counter-recoil mechanism for returning the gun to the firing position and keeping it
there,

and a counter-recoil brake or buffer

to soften the

shock as the

gun runs

into the firing position. Recoil brakes of the friction type were formerly used. Pneumatic brakes were also used to some extent. Both have been entirely

superseded by the hydraulic recoil brake. A hydraulic recoil brake consists of a cylinder filled with liquid and a piston. Relative movement is given to the cylinder and piston

by the

recoil,

and provision

is

made

from one side

for the passage of the liquid of the head of the

piston to the other, by apertures cut into the piston or in the walls of the cylinder. The power of the
lies in the pressure produced the cylinder by the resistance offered by the liquid to motion the area of the apertures is constant, it is

brake
in

FIG. A.

f through the apertures. evident that the resistance to flow will be greater as the velocity of the piston or the velocity of recoil is greater. Therefore, the pressure in the cylinder, which measures the hydraulic resistance offered, will vary with the different values of the velocity of recoil. If, however, the
!

apertures are constructed in such a manner that the area of aperture increases when the velocity of the piston increases, and diminishes when
that velocity diminishes, the variation in the area of aperture may be so regulated, that the pressure in the cylinder will be constant, or will vary in such a manner as to keep the total resistance to recoil constant, or
it

may

be

made

to

vary in
type- of

any manner
In figure

desired.

A

is

shown one

It consists of a hydraulic brake. cylinder on the inner circumference FIG. B. of which are formed bars of varying cross sections, called throttling bars (T), piston (p), and piston rod. Either the piston rod is secured to the carriage, the cylinder moving to the rear with the gun, or the cylinder is secured to the carriage, the piston moving to the rear inside of the cylinder. Through the piston head are cut slots or apertures through which the liquid is forced from one side of the piston to the other as the Each slot has the dimensions cylinder, or piston, moves in recoil. of the maximum section of the throttling bar with just enough clearance to permit operation. The area of orifice open for the flow of liquid at any position of the piston is therefore equal to the area of

the slots minus the area of cross section of the throttling bars, and

so determined that the resistance to the flow of the liquid, or the pressure in the cylinder, is made constant or variable, as desired.
is

In another type of hydraulic brake the throttling bars are not used, but the varying apertures are obtained by cutting grooves of varying width or depth on the interior of the cylinder. Figure B represents another method of varying the throttling The piston (P) is held rigidly from turning and the valve grooves. (V) is rotated by means of a spiral groove cut in the cylinder walls, in which the lugs of the valve slide during recoil, thus rotating the valve and varying the size of the openings through the valve and pisThis method is used to a considerable extent in British design. ton.
Figure C illustrates a method of central throttling. The throttling rod (R) has a varying diameter; this causes the amount of liquid,

which flows between

it

and the hole in the piston
correct throttling.

(P)

,

to

manner necessary for some French designs.
of the recoil,

This method

vary in the is used in

Counterrecoil, or the return of the gun to battery after completion may be effected by springs or by compressed air cylinders; the latter, in connection with the recoil brake, forming the hydro.
|

[

pneumatic

recoil

system.
of effecting
all

(V
|

c=

p^

~
\

The spring counterrecoil
gun
carriages

method

Z__
~f\

J

^~

may

be used in

on which the gun
These include pedestal mounts, all wheeled carriages as shown

recoils in the direction of its axis.

barbette carriages, turret mounts, and in figures F arid G.

In the smaller carriages of these types the springs, initially compressed to the desired amount, may be placed between the piston and the rear end of the hydraulic brake cylinder which is lengthened for that purpose.

In some carriages of this type the hydraulic brake cylinder moves with the gun in recoil, the piston being stationary. In such construcinder,

tions the springs are usually placed around the hydraulic brake cyland are compressed between a flange on that cylinder in front
of the carriage in the rear.

and some fixed part

In larger carriages the springs are arranged in separate cylinders with pistons of their own, two to four of these spring cylinders being required, see figures F and G.

shows a spring counter-recoil mechanism (spring recuperator) consisting of two concentric columns of springs. It is sometimes necessary to use telescopic springs as shown in figure E, when a single column would not allow sufficient recoil. These and other arrangements of counterrecoil springs will be further discussed in the description of the carriages to which they pertain.
Figure

D

34

AIR

RIS-TOM(FP)

H

IN-BA-TTETR^

OR F-|RNG

FLOAT-IMG PISTON

FIG.

K

IN-

BATTER V OR

F"IR>MC5 F>OS|-TlOrH

L- ElfSP OF f?ETCOILHVORO-PINEIUMATIC REZCQJL- S^
.

IM PIREICT

OOMTAOT WITH

THEI

WITH
>AIR

36

The hydropneumatic recuperator

(or counterrecoil

mechanism)

may

be separated from the recoil brake or the two may be combined in one unit. The principal advantages of air cylinders over spring cylinders for counterrecoil are the reduction in weight and longer life. These advantages are especially important in long-recoil field guns or howdesigned to be fired at high angles of elevation. If springs are used the columns are long and heavy, being liable to breakage; while if air cylinders are used, the additional pressure needed when the guns are fired at high angles of elevation can be obtained by pumping
itzers

more

air into

the cylinders.

It is evident that the energy, in whatever effects counterrecoil, forms a part of the total

way

obtained, which
recoil.

energy of

total resistance to recoil

is

composed

of the resistance offered

The by the

minus

brake, the resistance due to friction, the resistance either plus or due to the inclination of the top of the chassis or the recoil
slides,

and the resistance due to

M /L c
OIL

BX
^
"I

_
(w
L

JJ
J

the counterrecoil springs or air cylinders, if there are such included
in the recoil system.

FIG

M
is

The

counterrecoil buffer

is

pro-

carriage as the
recoil

gun

vided for reducing the shock to the returned to the firing position by the counter-

mechanism.

is shown a type of buffer which is used to some extent. In figure It consists of a rod (B) which acts inside the hollow piston rod of the

M

recoil cylinder. similar method to this is to provide a separate in which a projection of the recoil piston acts during the last cylinder few inches of recoil. It consist of a dash pot formed at the end

A

may

of the recoil cylinder. The use of the counterrecoil buffer increases the stability of mobile artillery carriages by preventing their forward motion as the gun

runs into battery.
recoil
field guns and howitzers are mounted so as to have a long on their carriages when fired horizontally. When certain types of these guns are fired at high angles of elevation it is necessary to reduce the length of recoil to prevent the breech of the gun from

Modern

striking the ground.

This reduction

is

effected

by

a

mechanism

which automatically reduces the size of the orifices in the hydraulic brake as the gun is elevated. This is known as variable recoil. If no counterrecoil buffer is provided, the velocity of the gun when going into the firing position under the action of the counterrecoil
springs or air cylinders
tion.
it
is

at a

maximum

just as

it

reaches that posi-

an arrangement is made to automatically fire the gun when has this maximum forward velocity, it is evident that the maximum
If

37
velocity of free recoil will be reduced

by the amount

of the

forward

velocity, and hence either the total resistance or the corresponding length of recoil, or both, can be materially reduced. Systems based upon this principle have been used abroad for small guns, such as

mountain guns. The gun is caught by a pawl in the extreme recoil When it is desired to fire, position and is loaded in that position. the pawl is tripped, the gun runs forward, and is automatically fired
as
it

reaches the firing position.

The

principal objections to this

system, which is known as the differential recoil system, are the unsteadiness of the gun at the moment of firing and the possibility of the gun being turned over in a forward direction by the shock of counterrecoil if a misfire should occur. In artillery of position, the gun carriage is rigidly bolted to a fixed
platform.
Its

mechanism

is

such as to allow the gun and the attached

The nydraulic brake cylinder and its piston parts to recoil on firing. are attached, respectively,, to the moving and fixed parts of the carriage, or vice versa, in

such a way as to cause the piston to be drawn the cylinder as the gun recoils. When constant total resistthrough is to be exerted by the recoil system, which is always the case in ance
artillery of position, either the total resistance or the length of recoil

be assumed, and the other determined. While the assumption very long recoil would reduce the resistance and consequently the strain on the carriage and permit its parts to be made lighter, the necessary increase in the length of the recoil slides might overbalance

may
of a

the saving in weight.

In carriages, such as mortar, anti-aircraft gun, and the latest type barbette carriages, all of which permit the firing of the gun at high angles of elevation, a very long recoil can not be used, because the distance from the breech of the gun to the supporting platform will not permit it. Furthermore, the use of a long recoil would necessi-

Lack

tate the use of long and heavy columns of counter recoil springs. of space also prevents the use of a long recoil on turret mounts.

In disappearing carriages, the length of recoil is determined more by the necessity of giving the gun the proper movement in recoil than by limitation of the strains brought upon the carriage. With the exception of the disappearing and the older type of barbette carriages, the recoil for artillery of position is comparatively
short.

The construction of all modern wheeled carriages is such as to allow the gun to recoil in the direction of its axis. The resistance to recoil developed by the recoil system pulls forward on the gun and
backward- on the carriage, tending to move the latter to the rear. Actual motion of the carriage to the rear is prevented by a spade sunk in the ground at the end of the trail of the carriage and so constructed as to present a broad surface to the ground in the rear.

38

Under ordinary conditions the ground will resist a pressure of 40 pounds per square inch of spade surface, and knowing the pressure developed by the pull of the piston rod, which is the only force acting on the carriage, the size of spade can be determined.
Another
effect

produced by the resistance to

recoil

is

a tendency to

rotate the carriage around the point of support of the trail, or to cause the wheels to jump from the ground. Such a movement is very undesirable, as it interferes with the rapid aiming and firing of

when

In order to prevent the wheels from jumping off the ground the piece. the gun is fired, it is necessary that the product of weight of the carriage including its recoiling parts and the horizontal distance

of the vertical through their center of gravity from the point of support of the trail, should at any instant be greater than the product
of the force opposing recoil

and the perpendicular distance from

its

line of action to the point of support of the trail. The value of the total resistance to recoil, that will be just insufficient to cause the

wheels to rise from the ground when the gun is in the firing position, obtained by equating moments which will show that a value of this resistance small enough to prevent jump of the wheels in the early part of the recoil might still cause jump toward the end of the
is

recoil, as

the

moment

of the weight of the recoiling parts

becomes

less.

evident that safety against necessary length of recoil shortened
It
is

total resistance,

we assume
line

it

jump can be maintained and the if, instead of assuming a constant as decreasing to such an extent as to

showing the maximum permissible values of the total resistance to recoil and plotted as a function of the length of If the length of recoil is such as to provide a factor of stability recoil.
remain parallel to a

when

the gun

is

fired at horizontal, the carriage will

be stable at

all

higher elevations, as the lever arm of the total resistance of recoil For this reason, reduction of the decreases as the gun is elevated. of recoil with increase of elevation in howitzer carriages does length

not affect their stability. The initial strength of the counterrecoil spring columns or air cylinders is the force which they exert. against the gun in the firing This force must be great enough to hold the gun in that position. at the highest angle of elevation at wilich it is to be fired, as position well as to overcome the friction on the recoil sides as the gun runs forward to the firing position.

AIMING DEVICES AND SIGHTING METHODS.
Sights will be discussed briefly in this pamphlet merely to indicate their application to field, anti-aircraft, and trench materiel.

In order that a projectile from any gun may hit the target, the gun must be fired at a certain angle of elevation depending on the
range, the ballistic characteristics of the gun, and
level of the

target. right or left of the target as to offset the deviation of the projectile due to drift and wind. The sights of the gun provide means of determining when the axis of the gun has the predetermined direction.

gun and

It

upon the relative must be given such a direction to the

the piece is sighted, both in elevation and direction by sighting directly 011 the target, the method is known as direct laying. This is precisely the same operation as sighting a shoulder rifle or pistol. The line of sight may be fixed in one of two ways. The first method is to use plain or open sights, the rear one of which has a
peep, or notch, capable of adjustment in a vertical or horizontal direction. This rear sight is equipped with an arc reading in frac-

When

be set

tions of the range, or degrees, by which the necessary elevation can off. In some cases the rear sight is designed to automatically correct for drift; if not, the drift must be set off on a scale provided

for this purpose

on the rear

sight.

It is

always well to bear in mind

that the projectile follows the movement of the rear sight, going higher as the sight is raised, and to the right or left as the sight is

moved to the right or left. The second method for direct
hairs

laying

is

to use a telescope

with cross
principle

which takes the place
is

of the

open sights although

its

of operation

the same.

The angle

of elevation of a

gun must be measured

in the vertical

plane through the axis of the piece. It frequently happens that a mobile piece must be fired under conditions in which the axis about

which

it turns in elevation (trunnion axis) is not level, thereby throwthe sight plane out of the vertical. If this is the case, the sight ing arm must be revolved about an axis parallel to the axis of the gun

until the sight

provision

arm is vertical. Most wheeled mounts have such made on their sights.

a

Independent Line of Sight. In order to relieve the gun pointer from the responsibility of setting the elevation on the sight standard and elevating the piece, some guns are provided with what is known as the independent line of It will be noted that the actual quadrant elevation of the sight.
piece consists of two parts: (a) The elevation necessary to reach the target same level as the gun.
(39)
if it

were on the

40
(6)

The

correction to this elevation required

by the

difference of

level of the

gun and target (angle

of site).

With the independent line of sight the two parts of the quadrant elevation are applied to the gun independently. An intermediate rocker and two elevating systems, and B, are provided as shown

A

in Figure N.

fixed to the rocker, and for direct fire the gun pointer the lower elevation system A, which moves the rocker manipulates as well as the gun in elevation. In this way the angle of site is autosight
is

The

matically corrected,
target.

when

the line of sight

is

brought upon the

The other elevating mechanism, B, is between the rocker and the gun and is manipulated by another cannoneer who elevates the gun
until the proper range appears on a range scale.

The change

in range does not

affect the setting of the

lower ele-

vating mechanism, and the gun
FIG. N.

pointer
,

is
.

thus free to devote his
.

whole time
sight

upon the target and is not compelled The above method has the objection, however, that telescope.
difficult to

to keeping his line of to take his eye from the
it is

make

the necessary correction in the range

drum for

differ-

ence in level of trunnion axis. Various modifications of this general method of securing the independent line of sight are in use and will be discussed with the guns
to

which they pertain. The gun is said to be

laid indirectly

when

it is

laid

by means other

than aiming directly through the sights at the targets. The fire from modern field pieces is so accurate and destructive
always necessary to establish field batteries in position out enemy for the sake of protection. Indirect sighting becomes then of necessity, the usual method of sighting such guns. The panoramic sight affords the means of aiming the gun in indirect laying by directing the line of sight on any object in view from the gun; at the same time it affords the advantage of a telescopic
that
it is

of the view of the

sight in direct or indirect aiming. This panoramic sight is a telescope so fitted with a rotating head, reflectors and prisms, that a magnified image of an object anywhere in

view

may

be brought to the eye without change in the position of

the observer's eye.

The panoramic sight is often mounted in connection with the range-sighting mechanism, but in some cases in order to divide the duties of laying for direction and elevation, the panoramic sight
is mounted on a shank on the left side of the cradle and used in laying for direction, while the range quadrant for laying in elevation

41
placed on the right side of the cradle and used by another cannoneer. In connection with the range quadrant a range level is provided, which is a special form of clinometer. It is used in setting off the angle of site, thereby correcting for difference in level of the gun or The range quadrant is graduated in degrees or in fractions target.
is

range (mils). In the case of howitzers, the different zones of fire are sometimes shown. While the use of the range quadrant separates the duties of the cannoneers in aiming, it does not comply with the conditions for the
of the

independent line of sight. The sight and range quadrant being attached to the cradle, both move in elevation with
the gun.

The independent

line of sight

permits of the gun being moved and setin elevation without any change in position of the sight used for direction

aiming.

Leveling plates or similar surfaces are provided on all guns and howitzers on

which a gunner's quadrant
the elevation.
It is
tail in this

(see p. 42)

can be used in obtaining or checking
not the intention to go into dehandbook regarding the fire-

control equipment employed for directing the fire of anti-aircraft materiel, but
as the

development

is

so new,

and they

PANORAMIC SIGHT, MODEL OF
1917.

are so closely involved with artillery
fire-control

during operations, it is quite necessary to devote some space to the equipment. Many of the terms and instruments used in connection with antiaircraft artillery are similar to those employed with field artillery

materiel, but the

methods
fire

of application in

most cases

differ.

anti-aircraft artillery the following angles in the laying of the gun to the predicted future position resulting of the target are involved.

In the direct

of

Present azimuth and elevation. sighting upon the target.
1.

These are obtained by direct

2. 3.
4.

Principal lateral and vertical deflections.

Secondary

lateral

and vertical

deflections.

Superelevation.

In the determination of the principal lateral and vertical deflections, two methods of fire control have been established: 1. Linear speed.
2.

Angular speed.

42

Each method assumes

rectilinear travel of the target,

i.

e.,

that

the pilot of the aircraft will fly a straight course at unchanging speed and constant altitude during the time required for the determination of the fuse range, setting of the fuse, loading and firing
the gun, and for the projectile to reach
its

point of burst.

Each

method

based upon sound mathematical reasoning and involves automatic apparatus of rather complex, but easily operated, mechanical and electrical design, in order to resolve the data required in
is

the laying of the gun. In the first method the quantities required in the resolution of the formulae are
:

GUNNER'S QUADRANT, MODEL OF
(a)

1918.

Presentation (angle of approach), i. e., the horizontal projection of the angle made between the vertical plane of sight and the axis of the fuselage of the airplane. (6) Engine speed of the target. (c) Altitude of the target. (d) Time of flight of the projectile to the future position of the
target.

The

resolution of the formulas

The readings ultiobtained from this instrument are given in mils. They are mately transmitted telephonically or by direct announcement to the gun layers who immediately lay the gun to its future position, while the

The great advantage of this method lies in the fact that the presentation and engine sDeed can be estimated with reasonable accuracy,. The altitude of the airplane is determined from altimetry stations, and the time of flight is known when fuse range has been determined
from a telemeter.
velocity of the target

In the angular speed method the lateral and vertical angular These are multiplied by the total is measured. element of time mentioned in the aforesaid and gives the respective displacements. The fact that the angular velocity of an airplane in ordinary flight is never uniform makes this method more difficult of apprehension but as applied in our instrument design gives results appreciably better than the linear s^eed method and is consequently used more generally. The instruments resolve the lateral and vertical deflection corrections in mils

and

are telephoned to the

gun layers who

These also the fuse range. function the sighting system

mechanisms. The element fuse range is required for two main purposes in antiaircraft gunnery: (a) For the setting of the fuse, and (6) as a function
i. in automatically giving superelevation to the gun e., the angle future position of the between the line of sight to the predicted target and the axis of the bore of the gun when ready to fire.

Secondary deflections are required in making allowances for windThese are set by giving secondary moveage, ballistics, drift, etc. ment to mechanisms of the sighting system. When firing, "indirect" or at night, which essentially is indirect
fire,

three elements pertaining to the predicted future position of the target are transmitted from this apparatus at the fire-control station

in order to
1.

accomplish the laying of the gun and setting of the fuse:

Azimuth.

2.

3.

Quadrant elevation. Fuse range.

Secondary deflections involve, in addition to those common to direct firing, corrections for parallax when firing "indirect." At night the alliance of listening apparatus and searchlights assist in accomplishing the resolution of the gun-laying elements at the
fire-control station.

Altimetry, which
cipal

is

a basic factor in the

and secondary deflection corrections,
:

is

computation of the prinobtained in one of two

ways
(a)

Monostatic.

or one-station instrument is an optical device that determines the altitude by automatic triangulation through the coincidence of light rays along a self-contained base.

The monostatic

44
(6)

Bistatic.

is a system in which two stations are set up and oriented a base line of known length, frequently as great as 4,000 along yards. The height or vertical distance of the target above the base

This

then determined geometrically by projecting its altitude horizontally into the vertical plane passing through this base line. When altitude has been determined, telementry, which involves
line
is

the functions, angle of
altitude, is readily

site, to

the future position of the target and

accomplished with the aid of automatic devices. When firing against airplanes at night, searchlights are used to illuminate the objective. When it is able to find it and keep it in its field, firing can be conducted in the same manner as in daytime. Many sound detecting instruments have been made one of
;

shape of a movable in azimuth and site, focuses the sound waves paraboloid, when its axis is placed in their direction they swing from one side of the focus to the other when the axis of the instrument is turned. The sound is received by trumpets placed on either side of the focus
the recent types
is
;

the ''Paraboloid."

A surface

in the

and joined in pairs to the ears of two observers who adjust the instrument, the one for azimuth, the other for site. Briefly, the foregoing describes the fundamentals of anti-aircraft
artillery fire-control methods. Being the most precise form of gunnery, anti-aircraft artillery involves material capable of the highest degree of facility and accuracy in the automatic measurement of deflections and the maneuvering of its gun-laying mechanisms in order that effective fire may be conducted against a target whose movements are subject to such large displacements.

ACCOMPANYING VEHICLES.
In addition to the piece
itself,

a

number

of vehicles are necessary

in batteries, sectors, and regimental organizations of field artillerj7 for maneuvering and serving the piece. The type of vehicles vary with the different guns and the various organizations. Some of the

more common vehicles such as limbers, caissons, etc., are described in a general way in this chapter, while their special features are described in detail with the materiel with which they are issued.
Other special vehicles such as reels, store and battery wagons, etc., are also described with the materiel to which they pertain. The caisson is essentially a conveyance for the transportation of

ammunition
nition

in the field.

mounted on two wheels and

It generally consists of a chest for axle. In front it is fitted

ammuwith a

short pole having a lunette for attachment to other vehicles and in the rear with a pintle, to which additional vehicles may be attached.

Various tools are usually carried on the caisson, and seats are provided for the accommodation of the personnel. The limber is a two-wheeled vehicle designed primarily to increase the mobility and faciliate the maneuvering and deployment of field There are several types of limbers in use, the principal artillery. ones being the carriage and caisson limbers. The carriage limber is attached to the trail of the piece when

For light field pieces, a chest for ammunition is protraveling. vided on the carriage limber. In the case of heavy pieces, the chest is dispensed with and the trail of the piece rests on the top section
of the limber.
traction,

A

pole

is is

and the rear

provided at the front for horse or motor equipped with a pintle for attachment of
is

the carriage. The caisson limber is used for hauling the caisson and with a chest for carrying ammunition.

provided

The forge and store limbers are designed to carry supplies and equipment, the forge limber carrying the tools and supplies for the farrie'rs shop. The battery wagon and the store wagon are twowheeled vehicles equipped with chests for tools, supplies, and spare
parts.

With batteries of heavier field artillery, some of the vehicles are dispensed with, especially the caissons, battery wagons, forge, and store limbers, the ammunition being carried in motor trucks, in which most of the spare parts and supplies are also carried.
(45)

46

47
Light
field artillery is

these batteries are
tractors or

now

drawn by horses although some of motorized, i. e., hauled by either caterpillar
usually

motor

trucks.

In addition to this, provisions are made for a limited number of trailers for use in carrying light guns at high speed behind motor
vehicles.

These

trailers are

rubber tired and for high-speed condi-

tions; the complete gun, with carriage, may be placed on this trailer instead of being transported on its own wheels.

The recent struggle in Europe brought about problems which heretofore have never existed in warfare; and to meet these changes have been made in every arm of the service, but the greatest and

75-MILLIMETER GUN CARRIAGE MOUNTED ON A 3-INCH FIELD GUN TRAILER.

most radical change being the motorization
transport
is is

of artillery.

Mechanical

at this time in such a state of of dwelling

no reed

upon

its

development that there numerous advantages over animal

draft.

origin aj x heavy artillery was limited to guns emplaced in permanent fortifications and guns of large caliber which were only moved with great difficulty. Light horse-drawn guns and howitzers

The

comprised the mobile
artillery

artillery for use in the field.

This type of

was

ideal for quick action at short ranges.

As the

artillery

range guns were required. 4 18322820

became a more important factor, large caliber longThe movements of this heavy artillery in

48
the field could only be accomplished in one way by motorizing The result is the development of the extremely mobile heavy
artillery.

it.

In applying motor transportation to

artillery,

types of motor

vehicles of widely varying capacity and duty are required. In most cases commercial cars and trucks are used, but in a few instances

have been developed. Motor equipment is still undergoing changes, all tending to produce apparatus of unfailing dependability and maximum mobility and flexibility. Motor apparatus of the following types have been selected as the most suitable for accomplishing this motorization: First, passenger cars, both light and heavy; second, motor cycles with and without side cars; third, trucks; fourth, four-wheeled trailers: and fifth,
special types

tractors of the caterpillar type. Passenger cars are furnished

when on

the

march and when occupy-

Batteries are supplied with light touring Battalion and registaff cars, and motorcycles with side cars. cars, mental headquarters are also supplied with light touring cars and

ing a position on the lines.

Westfield military bicycles. motorcycle is ideal for liaison and work of similar nature requiring rapid transportation for one or

A

two individuals. The motorcycle is particularly useful when traveling in convoy and for keeping the various units of an organization
in close

touch with each other.

Motor trucks are necessary for carrying supplies and ammunition from the depots and distributing them to the various units. A great many trucks are required to insure unfailing supplies when artillery
is

in action.

Because of 'the uncertain conditions of the roads back

of the lines sturdy trucks that can pull through under the most unfavorable conditions are employed.

In bringing the guns into position it is often necessary to cross ground plowed by exploded shells, to go through mud and deep sand. and to ford streams which can not be negotiated by a wheeled type of motor vehicle, thus the type of apparatus adapted for this purpose
the caterpillar tractor. The problem of the care and maintenance of motor equipment in the field is met by issuing the repair and artillery supply^ trucks to
is

each battery supply and headquarters company of motorized artillery. The artillery supply truck is really a motorized store wagon carrying spare parts, tools, etc., for the particular kind of unit to which
it is

assigned.

The
on
air

artillery repair truck consists of a small machine shop mounted wheels. Its equipment is complete, including a lathe, drill press,

forge, etc. Electric power is supplied by a small gendriven by an individual gasoline motor mounted on the truck. erator

hammer,

49

The equipment

is

designed to

make

all repairs in

the

field,

both to

and motor vehicles. The motor equipment makes transportation a comparatively easy matter, permitting it to be moved with rapidity, either on the offensive or defensive. The value of this equipment becomes more apparent
artillery materiel

as the nature of warfare changes

from that of position

to that of

movement.
Detailed descriptions of the above motor vehicles are given in separate handbooks pertaining to motor equipment materiel.

37-MILLIMETER GUN MATERIEL, MODEL OF

1916.

Experience has shown that the infantry can not carry out its by its own weapons, except at prohibitive less of personnel. Our automatic rifle is practically useless for ranges greater than 500 meters, and then only against personnel. The individual rifle does not offer the necessary volume of fire, while the rifle grenade, and even more so, the hand grenade, is a clcse combat
mission,

weapon.
sisting of

Hence the taking
an automatic
rifle

of a

machine-gun nest by a unit (con-

squad, hand bombers, and rifle grenadiers) attacking the flanks, will not prove very successful, particularly are echeloned to considerable depth, and if machine-gun nests executing cress fire. Such conditions calls for some form of artillery, effective at from 400 to 1,500 meters, against both personnel and materiel, raid

37-MILLIMETER GUN CARRIAGE AND AMMUNITION CART, LIMBERED.

capable of immediate action. The field artillery is not available because of difficulty of communication and length of time necessary to get into action. The heavy artillery is not sufficiently
mobile.

by

Its dispersion is too great for small, definite targets, therecalling for vast amount of ammunition, extremely difficult to

transport.

The

necessity of providing an accompanying

gun

for certain units

of infantry has led to the adoption of a 37-millimeter

gun

(devel-

oped by the French Army)

.

The 3 7-millimeter. gun, also known as the 1 -pounder or infantry accompanying gun, is the smallest weapon of the field-gun type in use by the American Army. It is used by advancing infantry
outfits, chiefly for

destroying concrete machine-gun emplacements, and other points of resistance. Recent developments outposts, and modifications of this weapon have found wide application for
(50)

51

52
its

.

use and, due to its extreme portability, this gun is adaptable for tanks, tractors, and aircraft. As this gun is intended to follow infantry over any kind of ground,
construction
is

its
is

designed to give great mobility.

The personnel
is

organized for rapid fire; the possible rapidity of fire
:

35 shots

per minute.

Each gun unit is composed essentially of two elements (1) The gun on a tripod mount, capable of being set on wheels. (2) A light wagon serving as a limber and carrying ammunition,
spare parts, and accessories. The gun and limber when joined are normally hauled by one horse or mule, but near the enemy they are separated and moved

by man.
In action the gun is operated by two men, one keeping it on the aiming point and the other loading and firing. The gun must be cocked by hand in order to load for the first round, but thereafter the counterrecoil of the barrel cocks the piece, and it is only necessary to open the breech mechanism, which ejects the case, insert a new cartridge, close the breech, and fire. When used as a tripod mount, it is separated into portable groups for transportation and each unit is carried by two men. One group, weighing 104 pounds, consists of the gun and cradle and the other of the trails, weighing 84 pounds. With the combination tripod mount, the gun is transported on a wheeled carriage which is limbered to a two-wheeled ammunition cart, drawn by one mule or horse.
Weights, dimensions,

Weight of axle, complete Weight of wheels, each Weight of trails (including pintle and Diameter of wheels

pounds
float)

.

.

25
68

do do
inches.
.

84
37. 75

Width of track Weight of gun and

do
carriage,

33
.

complete

pounds.
inches.

360
75

Over-all length of vehicle Over-all height of vehicle

.

do
. . .

37.75
.

Over

all .vidth of

vehicle

.do.

57

53

The gun is composed mainly of a steel alloy barrel. A front clip bronze and an aluminum jacket serve as supports and guides for the whole barrel. The breech housing is screwed to the rear end of the barrel and forms a receptacle for the breechblock. The breechblock is of the Nordenfeld type and with the exception of size is practically the same as that used on the French 75 millit screws into the breech housing and is opened meter field gun. and closed by being rotated 156 degrees about its axis, which moveof
J

The breechblock is is limited in each direction by a stop. cylindrical in form, rotates in a threaded seat and is operated by a handle which when moved to the left causes the eccentric hole in
ment
the block to register with the bore and also operates the extractor thus ejecting the empty cartridge case. Pulling the lever to the right rotates the block so that the port in the block is drawn away from the bore and a solid surface containing the firing pin backs up
to the base of the cartridge. The action of the powder gases on the breechblock at the moment of discharge produces the recoil of the united barrel and breechblock.

TRIPOD MOUNT

IN FIRING POSITION.
is

The purpose
and

of the recoil

mechanism

to control

and limit the

recoil

to return the barrel to the firing position, at the same time preventing a sudden return which might disturb the aim of the gun.

The recoil cylinder consists of a cylinder containing a piston, piston valve, counter recoil spring in three sections, and counterrecoil buffer. The piston rod, which is hollow and open at the piston end,
is

counterrecoil.

oil both during recoil and with four holes for the passage of oil during recoil. This oil is allowed to pass through two parts of the piston; first, through the hollow portion of the piston rod, and

pierced with holes for the passage of

The piston

is

fitted

second, through the holes in the piston head. the piston head are closed by the piston valve.
in the

The oil passages in The valve is held

against the front face of the piston by a spring, closing the oil holes head during the counterrecoil stroke, thus slowing up the for-

ward motion

of the gun. The counterrecoil buffer is screwed into the front cylinder cap and eases the movement of the gun into The capacity of recoil battery, thus preventing excessive shock.
is

cylinder

2.75 pints and the extreme travel of piston

is

11 inches.

54
be used either in the form of a tripod or with the n the former case a front leg having a float adjustable to two heights at its lower end is used to support the front end of the mount, and the spread trails in rear equipped with n the case of the wheels spades form the other points of support. the front leg is swung up and secured, and both trails being used, are spread out to support the rear.

The mount

may

axle and wheels attached.

The
being

pintle, or
fitted

gun mount,

is

in the

form

of a yoke, the

to receive

the cradle trunnions.

Each

equipped with lugs which pivot on bearing surfaces in of the pintle. The trails, when spread, are kept in position by a removable transom, which also serves as a seat for the gunner. A Y-shaped frame, pivoted and secured to the pintle at its upper and lower ends, extends to the rear in the form of a fork and engages the nut housing on the traversing screw. The nut is turned in its housing by a small handwheel attached thereto, w^hich causes the

upper end head is the lower end
trail

GUN DISASSEMBLED ON THE MARCH (WHEELS AND AXLES LEFT

IN

THE REAR).

nut and housing to move along the screw, thereby traversing the The screw is pivoted in the left trail and moves in and out through a bushing pivoted in the right trail when the trails are being spread or closed. When the trails are to be closed, the gun is traversed to the extreme right. The elevating mechanism is located on the frame in front of the A screw fitting into a nut pivoted in the traversing mechanism. frame is raised and lowered by a handwheel attached to its upper end. Above the elevating handwheel is a hook engaging a pin fitted to the underside of the cradle, thus the rear end of gun is secured to the trail and the elevation accomplished when the cradle is mounted
gun.
in the trunnion bearings. A conical sheet metal flash hider
is

secured to the muzzle of the

gun.

these carriages are equipped with an armor plate The shield consists of three shield, suitably reinforced by stiff eners. plates hinged together, and is mainly employed to protect the gunners
of

Some

from shrapnel and flying fragments.

55

The gun

is

provided with a telescopic sight for use in direct

fire

and a quadrant sight for indirect or masked |ire, either of which is mounted on the left side of the gun and in a bracket which is part of
the striker rod housing. The wheels are 37.75 inches in diameter and have steel tires 1.875 inches in width.

The ammunition
ing 1.097

is

of the fixed type

having a

steel projectile

weigh-

pounds containing high explosive, and detonated by a base percussion fuse. A complete round of ammunition weighs 1.47 pounds and is composed of projectile, brass case, primer, and

powder charge.

^ r

GUN AND PERSONNEL ON THE MARCH (AMMUNITION CART LEFT

IN

THE REAR).

AMMUNITION CART FOR THE 37-MILLIMETER GUN.
The 37-millimeter gun limber (of the machine gun ammunition wagon type) is essentially a frame resting on two shafts having a movable bolt and rear fittings by means of which it can be joined
to the

The 1-pounder semiautomatic gun and carriage was primarily intended for landing purposes, but it has been used in trench warfare and to accompany infantry troops. This equipment is well adapted to the latter uses, due to the fact that its weight is such, as to permit it to be readily transported from place to place by man power. The gun is made of nickel steel, with the gun body and breech end being forged in one piece. The breech mechanism is of the Bethlehem semiautomatic type in which the breech is opened, the case The block is ejected, and the firing pin cocked on counterrecoil. closed by a spring which is compressed during counterrecoil and
held in that position by the extractor until tripped of another round.

by the

insertion

and consists essentially of a and axle. The cradle supports the cradle, pivot yoke, trail, wheels, gun, forms a housing for the recoil mechanism, and is itself supported by trunnions bearing on the pivot yoke. The recoil mechanism is located above the gun and consists of a hydraulic cylinder and counterrecoil springs. No elevating and traversing mechanisms are as the laying can be readily accomplished by means of a provided shoulder guard and grip. Open sights are furnished and a bullet proof armor plate shield
is

The carriage

of the long recoil type

affords protection for the cannonneers.

Fixed ammunition is used, and is packed for transportation in steel boxes containing 60 rounds each. A hand cart for carrying four boxes, 240 rounds, is issued, the front and lid of this cart, being bullet proof.
Weights, dimensions,

The 2.95-inch Vickers-Maxim mountain gun materiel, is of Vickers design and American and British manufacture. This materiel is intended for transportation by pack animals; for this reason it is a
compact weapon, separating very quickly and easily into four loads for packing. The cradle is carried as one load, the wheels and axles as another,
light,

Four other pack animals the trail another, and the gun as the fourth. carry the pioneer tools, blacksmith's tools, supply chest, and signal Additional pack animals are employed to carry tools, respectively.
the ammunition for the battery. Suitable pack frames with all the necessary attachments are provided for holding the load compactly and in proper place on the animal.
Weights, dimensions,

barrel is a one-piece steel forging, cylindrical in form. end two lugs are provided to which the

ward

Forpiston rods are secured when the gun is mounted in the cradle. of these lugs is a finished surface of uniform diameter which constitutes a bearing for the gun. This surface is supplemented at

the forward end of the gun by two collars of equal diameter, thereby insuring a firm bearing for the gun in the cradle, either in recoil or in battery. At the bottom of the barrel is a guide which slides in a
(59)

60
corresponding groove in the cradle, thus keeping the gun in proper position and preventing it from turning when in action. The breech mechanism is of the interrupted-screw type. A handle which swings from left to right turns and swings the block clear with

The firing pin is operated by means of a trigger which by the firing lanyard. A safety device is incorporated to prevent firing when the breech is not closed. The breech is equipped with an extractor which ejects the empty cartridge case after firing.
one motion.
pulled
is

61

The recoil mechanism is of the hydrospring type. It is known as the short-recoil type in which the gun is permitted. a length of recoil upon the carriage, sufficient to diminish the movement of the carriage on the ground but not sufficient to render the carriage stable.

To

z 3
(5

y

retard the movement of the carriage on the ground the wheels are " locked by means of brake ropes/' which lock the wheels to the trail. Two buffer cylinders, one on each side of the gun, are bored in the cradle casting. They contain both the recoil and counterrecoil mechanism. The cylinders are connected at the rear by a by-pass

which keeps the

oil

pressure equal in the two cylinders.

Throttling

62
is

obtained by grooves of varying width in the cylinder liners. The piston rods are attached to the gun by means of interrupted screws,

which permit quick removal for transportation. The counterrecoil mechanism consists merely of springs wound around the piston rods, which are compressed on firing and which
return the gun into battery.

REAR VIEW OF CARRIAGE.
cradle is a bronze casting comprising three parallel cylinders. central cylinder supports the gun from the breech to within a few inches of the muzzle. The other two, as before stated, accommodate In place of trunnions there are two lugs the recoil mechanism.

The

The

underneath the cradle through which passes the cradle axis bolt, by means of which the cradle is secured to the trail. This bolt is provided with a handle and suitable catch for quick removal when disassembling for packing. The cradle also carries the sight bracket

63

and has a plane surface on
be used.

top,

on which the gunner's quadrant

may

The elevating gear consists of a quadrant with a worm wheel segment thereon operated through suitable gearing by a handwheel on the left side of the trail. A bolt for quick release of the elevating

eye

pi5fan

lock.

DETAILED VIEW OF GUN.

mechanism from the cradle

is provided. Elevations from 10 degrees depression to 27 degrees elevation may be obtained. No traversing mechanism is provided, and transverse must there-

fore be obtained

by swinging the

trail.

e/sra//**

/breech

SIDE VIEW OF CARRIAGE IN BATTERY.

The trail consists of two steel side plates connected by crosspieces and transoms. The front crosspiece contains bearings for the axle, cradle axis bolt, and elevating gear. A shoe at the rear end of the trail is fitted with a "scraper," which in reality is a short spade. It is also provided with a socket for the handspike. 18322820 5

64

The

axle is a solid cylindrical
it in

bar with

flats

cut on two sides for

It is quickly removable the front crosspiece of the trail. securing for packing and is carried on the same pack animal as the wheels. The wheels are 36 inches in diameter and are steel tired.

Sighting is accomplished by means of the sight, model of 1912, combined with either an open sight or the panoramic sight. The sight shank is a steel arc which can be moved up and down in elevation by means of a scroll gear. A range strip on the rear face of
the arc
is

graduated

in

50-yard divisions up to the

maximum

range

of the piece.

Combined with the sight is a graduated level which serves the same purpose as the range quadrant used on the 3-inch equipment and other
materiel of that type.

By this means the piece is laid for elevation. mounted on the left side of the cradle. By ha\ ing the quadrant level and sight thus combined one man can lay for both
The
sight
is

elevation and direction.

The ammunition used is of the fixed type, consisting of the steel high explosive and shrapnel shells, each weighing 12 J pounds. Each animal carries two chests containing five rounds each.

75-MILLIMETER GUN MATERIEL, MODEL

1916.

The United States model 1916, 75-millimeter field gun is an adaptation from the United States 3-inch field gun, model 1916, arranged
with a split trail and having greater traverse and greater elevation than either the French or British models of this caliber.

The 75-millimeter
mobile
as large as

field artillery of

gun constitutes the light artillery or rapid Army. The caliber of the piece is about horse-drawn mobility will permit. The caliber is ready
field

the

FRONT VIEW OF CARRIAGE.
equivalent to 2.95 inches, and was adopted by the French and by the Italians, while the United States had adopted the caliber of 3-inch and Great Britain a caliber of 3.3-inch, which is the caliber of
their 18-pounder. The German caliber was 77 millimeters, equivalent to 3.03 inches. The points of excellence obtained from these

types

are accuracy, long range, rapidity of

fire,

ease of transportation,

and

smooth and

reliable functioning.

the range depends not only on the power of the gun and on the design of the ammunition but on the elevation provided for, and
(65)

As

66

tat

8

:

II

I

e

LJ

O 2
cr

CD

02

ok
=>

LJ O O -r O

-

,

lO

68

which could be covered by a gun with a single governed by the permissible traverse, great attention was given to the mechanical features covering the vertical and horizontal limits of the gun laying, as well as to the smooth and reliable functioning of the piece. Of the above models, the French model is credited with functioning most perfectly, but the United States completed a new carriage which permits very high elevation of the gun and wide traverse. Due to the permissible elevation, the American piece outranges the French, although the French gun has a greater muzzle velocity. Roughly, the weight of the piece, including the carriage and limber, is about 4,600 pounds, which in general corresponds with the horseas the horizontal afc
setting of its trail
is

drawn

draft limitation over rough ground of 765

pounds per animal,

REAR VIEW OF CARRIAGE
calling for six horses to the piece, although four horses are frequently employed over level or hard ground.
of motor tractors has altered the draft problem, remains the question of facility in handling the piece by man power after battery position has been reached. As illustrative of this it may be mentioned that the weight at the end of a 75-millimeter gun carriage trail is in the vicinity of only 100 pounds. The trails can be readily unlimbered and spaded into position or its position changed by man power within a few moments, while to unlimber and spade into position or to change the position of the

The introduction
still

but there

trail of a 155-millimeter gun requires the use of jacks and a considerable expenditure of time. Rapidity in moving a fieldpiece from point to point, where railroad transportation is not available, is not entirely a matter of the speed

of the tractor, for likelihood 6f damage to the materiel when transported at high speed on its own wheels must also be considered.

69

The dimensions and weight

being placed on transported at high speed behind a motor vehicle. The movement of the light artillery is of utmost importance, and the 75-millimeter field gun may be considered as a gun of first rank, for This weapon it constituted the light artillery of the military powers.
is

of the 75-millimeter piece permit of its a rubber-tired trailer, which allows of its being

accurate, has a range

up

to 6 or 7 miles,

is

suitable for the projection
tear,

of high explosives, shrapnel, incendiary,

smoke, asphyxiating,

tracer, illuminating, terrorizing, and chain projectiles, and is adaptable for barrage fire, destruction of personnel, tearing away of wire entangle-

ments, destruction of fair-sized obstacles, and to some extent the
destruction or protection of lines of communication. The indications are that a slightly larger caliber will supplant this caliber in order to obtain longer range and greater destructive force and either motorization or direct

mounting on self-propelled

caterpillars

may

affect the

LEFT SIDE VIEW OF CARRIAGE.

adoption of a new caliber, for mobility and rapidity and ease of handling are features of importance in this branch of the field artillery.
Weights, dimensions,

Length of recoil of gun on carriage (variable) Height of axis from ground

do do ....
degrees.

18-46
53
7

do. ... 41. 625
.

Maximum angle of elevation Maximum angle of depression Maximum traverse, each side of center Maximum angle of elevation with angle of site handwheel. Maximum angle of depression with angle of site handwheel
.

do
mils
..

.

.

400
11
7

degrees. do. ...
.

75-MILLIMETER GUN AND CARRIAGE, MODEL OF
(AMERICAN).

1916

and consists of a tube, breech hoop, and clip. There are six slightly jacket, locking hoop, varying types of this gun, but the variations deal only with the manner of attachment of the jacket and locking hoop and do not The gun is guided in recoil by two affect the general dimensions. on the lower sido of the jacket. A lug on top near the forflanges ward end of the jacket containing a T-slot, holds the forward end of
The gun
is

of the built-up construction

the recoil cylinder. A short hoop or clip

is shrunk on the tube near the muzzle and under side two lugs which form guides for the gun on Provision has been made to prevent dust from entering cradle. tween the surfaces of the guides and their bearing surfaces on

has
the
be-

on

its

the

cradle.

The breech ring, which screws to the rear end of the jacket, forms a housing for the breech block which slides up and down with the The ring carries at the top a lug to which the action of a wedge. hydraulic recoil cylinder is secured, and at the bottom another to
which the two spring piston rods are attached. The breech block is of the drop-block type and operates semiautomatically, in that the breech closes automatically when a round it is opened by pulling back a handle on of ammunition is inserted, the right side of the breech, which not only slides the breech block out of place but operates the extractor, thus ejecting the empty carWhen a round is inserted smartly into the breech, its tridge case. rim strikes against the lips of the extractor causing the mechanism to The cartridge primer is close under the action of the closing spring. fired from the left side of the carriage by a continuous-pull firing mechanism. The firing pin is cocked and fired by one continuous backward motion of the firing handle. The carriage is of the split-trail type which means that the trail is made up of two halves, each being hinged to the axle near the wheels and capable of being spread out at a wide angle or brought together This feature permits at the spade ends and locked for traveling. elevation and traverse than the ordinary type of trail and greater
reduces the necessity of shifting the of 50 mils or more are desired.
trail

when changes
trail,

in deflection

A

seat

is

provided on each half of the

the one on the left for

operates the sights, the traversing and angle of site and fires the piece, and the one on the right for a canhandwheels, noneer who sets off the range and angle of site and operates the
the gunner

who

breech mechanism.
(71)

73

I

SSi

74

The

recoil

mechanism

is

of the hydro-spring variable recoil type

consisting of one hydraulic and two spring cylinders which comprise the recoil and counterrecoil mechanisms. On account of the high

angles of elevation at which this gun can be fired,

it

was necessary

to design a variable recoil system by means of which the length of recoil of the gun would be automatically lessened, the higher the

muzzle

is

elevated.

This

is

accomplished by means of a valve turn-

ing in the cylinder and shutting off or opening a number of holes, proportional to the elevation, thus making the resistance to the

passage of the

oil

greater or

less.

GUN AT MAXIMUM ELEVATION. The angle of sight mechanism consists principally which is moved by two hand wheels, one on each side
of

a rocker

of the gun.

Movement

of the mechanism causes the gun, cradle, elevating mechanism, and sights to move also, they being connected to the rocker. The handwheel on the left or gunner's side is used when laying for direct fire, or in other words, when site is set independent of range. The angle of sight scale is graduated in mils. All settings on the

angle of sight scale are set

oft'

this being the normal setting when the axis of the target are in the same horizontal plane.

above or below the 300-mil graduation, bore and the

The elevating mechanism used in setting the range is mounted on the rocker, and therefore independent of the angle of sight mechanism? the gun and cradle only being moved upon operation of the handwheel.

The range

scale

is

graduated in meters.

brakes are used on this carriage and are operated by a hand lever in rear of the shield when in battery position and by a lever

Band

from the axle seat when

in traveling position.

75

76

The gunner and cannoneers are protected by the customary shields and apron. The sight used is of the model of 1916 type, which provides a support for the panoramic sight and the peep sight. Wooden wheels, 56 inches in diameter, with steel hubs and tires, are These wheels are interchangeused, the tires being 3 inches in width. able with those of the caissons and limbers. Fixed ammunition is used in the 75-millimeter field guns and is made

up of either common shrapnel or common steel shell. Shrapnel rounds are issued with the projectiles filled and fuzed; the shell rounds are issued filled but not fuzed and contain an adapter with
booster charge.
projectiles average in weight: Shrapnel, 16 pounds, fuzed; The components of one round are the shell, 12.3 pounds, fuzed.

The

cartridge case with primer,
shrapn.el,

powder charge, projectile, and fuze in and adapter and booster in the shell. Weight of powder
1.5

charge

is

approximately

pounds.

CARRIAGE AND LIMBER

IN

TRAVELING POSITION.
is

A battery of 75-millimeter gun carriages, model of 1916, panied by the following vehicles
:

1 Cart, model of 1918. The above gun carriage was originally the 3-inch gun carriage, model of 1913, which was later called the 3-inch gun carriage, model of 1916. The gun was afterwards modified to caliber 75 millimeters, as was the 3.3-inch British, thereby permitting interchangeability of ammunition with the French guns.
1

of 1909

For horse batteries the battery Ml with the cart, model of

reel,

model of 1917, is issued. For motorized batteries the reel, 1918, is issued in lieu of the battery reel, model of 1917.

hydropneumatic recoil and a standard 75-millimeter gun The new materiel will be known as the 75-millimeter gun weight. materiel, model of 1916 ML

mechanism

in place of the hydrospring type, modified and fitted with a counter-

The St. Chamond recoil mechanism as adopted for these carriages was developed during the war in 1917 by Col. Rimailho, of the French Army. This mechanism, of the hydropneumatic type, is durable and smooth in operation. The use of small cradle forgings was made
possible

by

recoil cylinders.

the introduction of high pressures in the recuperator and In order to hold these pressures, it was necessary

to develop suitable packing, and the success of this recoil largely due to the design of these packings.

system

is

The

St.

Chamond

recoil

mechanism

consists of three cylinders, the

middle one being the recoil cylinder, the right cylinder having an air reservoir at its forward end, and an oil reservoir at its rear end; the left cylinder, known as the recuperator cylinder, has at its forward end an air space, and at its rear end a floating piston and regulator
for controlling the length of recoil. The recoiling parts are held in battery

by

the reaction of the air on

the floating piston transmitted through the liquid against a leakIn recoil the gun moves to the rear, carrying with tight recoil piston.

The energy of recoil is absorbed the recoil piston (middle cylinder) the throttling of the oil through a spring-controlled orifice in the by regulator valve. An opening is provided between the recoil and the recuperator
it
.

During recoil, the pressure in cylinders to house the regulator valve. the recoil cylinder opens the regulator valve, the movement of which The oil passis controlled by a helical spring and Belleville springs. the orifice controlled by this valve moves the floating ing through to piston forward against the air pressure, thereby storing up energy return the gun from the recoiled position to its position in battery. The valve in the counterrecoil orifice remains closed during recoil.

The The

which consists

throttling during recoil is controlled by the regulator valve of two parts, an upper stem and a lower valve stem. lower valve stem is seated on a circular seat at the entrance
?

channel to the valve.

As the valve
(78)

lifts,

the throttling area becomes

79
In the Vertical circumferential area between the valve and its seat. long recoil the movement of the valve is controlled by a spiral spring which reacts on the lower valve stem. The upper stem rests in a valve housing and has Belleville springs reacting on the stem only. To

move
ally

by

the upper valve stem, the whole housing is lowered automaticAt short recoil, a cam operated by the elevation of the cradle.

the upper stem of the regulator is brought down by the cam until its lower surface is in contact with the top surface of the lower valve

stem

in order to control the throttling of the valve.

The regulator valve is closed during the counterrecoil movement. The oil flow during counterrecoil is different from that during recoil,
the counterrecoil flow path being through a small channel beginning at the inside end of the buffer chamber in the recuperator cylinder and finally emptying into the recoil cylinder. The throttling during
counterrecoil takes place through a constant orifice located at the beginning of the counterrecoil channel. The tapering buffer rod on

the floating piston in the recuperator causes additional throttling through the small annular area between the buffer chamber and buffer

rod of the floating piston, which brings the recoiling parts to rest without shock.

18322820-

6

75-MILLIMETER GUN MATERIEL MODEL OF
(FRENCH).

1897

Ml

The -French 75-millimeter field gun adopted for the service of the United States dates back to 1897, when it was perfected by the French Army. The French model 1897 field gun has fired, on test, as high as 30 shots in a minute, and it is understood that the American model 1916 equaled this rate; likewise, a St. Chamond gun with interrupted screw-type breech on the special St. Chamond recuperator. Apart from the personnel service to the piece, the length of time which either gun could maintain this rate of fire, or any other rapid rate of fire, is perhaps not definitely determined. As to whether or not such length of time would be limited by the heating of the gun or by the heating of the recoil mechanism is likewise perhaps not definitely
determined.

Rapidity of firing is of vital importance, for it is self-evident that under certain conditions a gun which can fire twice as many shots per minute as some other gun is, for the moment, equivalent to two guns of the second class. Rapidity of firing action is dependent

upon the arrangements involved for the sighting, maintaining of the gun on its range, loading, firing, time of recoil and return of the gun to battery position, opening of the breech, and ejection of the empty
cartridge case.

For

artillery of position a great part of the

enormous energy

re-

quired to start the projectile on its way may be absorbed by a heavy foundation furnished as a mounting for the piece. An efficient recoil

however, of vital importance in connection with light owing to the essentially light weight of the carriage on which the gun is mounted, to permit of its ready mobility. The recoil mechanism not only absorbs the greater part of the recoil energy of the gun, but it returns the gun to the battery or firing position, and to be efficient it must be able to perform these two functions quickly, smoothly, surely, and continuously. The word " surely" is used in the sense of firmly and without shock, and of The recoil mechanism not only takes up the recoil being reliable. but it forces the gun all the way back into battery, or to a position within the variation which the design permits, under all conditions
is,

mechanism

artillery for field service,

of elevation

and heating. The general theory of hydropneumatic
In
its

recoil

mechanism

is

not

new.

relation to light artillery its most notable exemplification in battle has appeared in the Puteaux Arsenal type of the French
Its virtues

piece.

have been widely heralded and every
its

effort

has

been made to keep

construction secret.
(80)

Its several parts

were

81

32

83

were assemfew persons were admitted to this room. In the agreement, to manufacture of the complete recuperator in the United States, it was stipulated that the greatest secrecy should be maintained with reference to its design, manufacture, and assembly. There is a difference between land and naval warfare, in this respect: In a duel between two large fighting ships of equal speed to insure their remaining in contact, the one with the heavy, longrange guns has the other at its mercy, as it can destroy both its opponent's base and at the same time its opponent's personnel by sinking the opponent ship. In a land battle, the fortifications may be reduced by the long-range gun, of heavy caliber, but it is the destruction or capture of personnel which brings a war to an issue and the personnel may move to open country and open order, under which conditions the heavy, long-range gun, which is expensive to construct, slow and difficult to transport, expensive to fire, and withal short of life, no longer has a great target on which its tremendous energy may be concentrated. Land warfare has clearly demonstrated that it is the killing and manufactured
bled in a small
disabling of personnel or the capture of enemy troops in large numbers which far outweighs the capture of cities or of terrain which
is

at different points in France and these room at the Puteaux Arsenal, and but

nonproductive of raw material, in the forcing of an issue. This 75-millimeter gun was most effective in the open-country fighting, in the protection of troops and in working havoc among enemy troops

and bringing in prisoners formation.
Caliber

by creeping barrage
and

laid

behind an enemy

Weights, dimensions,

ballistics.

millimeters.

.

75

Total weight of gun and breech mechanism Total length of gun Rifling, uniform, right hand, 1 turn in 25.6 calibers.

angle of elevation angle of depression Total traverse of carriage on axle Weight of the carriage, complete (without gun)

19

do do ...
pounds.
do.
.

10
6
.

1,

642

Weight

of

gun and

carriage, fully

equipped

2,

657

84

85

86

75-MILLIMETER GUN AND CARRIAGE, MODEL OF

1897,

Ml (FRENCH).

The gun is of the built-up construction type, consisting mainly of a steel tube reinforced at the breech end with a breech hoop and
covered in the central portion with a bronze jacket. The total length from face of breech to muzzle is slightly less than nine feet. The recoil lug under the breech carries the coupling key, which connects the gun to the recoil mechanism. A safety pin operates between the breechblock and the coupling key, so that it is impossible to close the breech and fire the gun when it is not securely locked to the recoil mechanism of the carriage. On the underside of the gun are inclined bronze slides which are in contact with similar slides on the recoil mechanism. Rollers are also attached to the gun, and during recoil the gun first slides on the inclined guides and then the rollers lift the weight off the slides, the remainder of the travel being on the rollers. A pair of rollers at the muzzle permit a long recoil with short guides by taking the

overhanging weight when the gun is at full recoil. The 'breechblock is of the Nordenfeld type, cylindrical in shape and threaded on the outside. It is opened or closed by the operating handle from the right side of the gun by the same man who sets the
for range and fires the piece. Opening the breech' automatically actuates the extractor, which in turn ejects the empty cartridge case. The round of ammunition is fired by a striker which is driven for-

gun

ward by a spring-actuated hammer pulled by the lanyard. The carriage is very compact and simple, consisting of a housing around the axle, above which is the support for the cradle, and a box section trail ending with the customary spade and lunette Seats are provided for two men, the one sitting on the right side operating the range scale mechanism, opening or closing the breech and firing the piece; the man on the left sighting the gun and operating the angle of site and traversing mechanisms. The reccil mechanism is of the hydropneumatic, long recoil type and contains both recoil and counterrecoil mechanisms. A gage
plunger
is

indicates that

located in the rear end of the cradle which, when flush, more oil should be added until the plunger projects
Oil

about

f inch.

may
a

side of the cradle

by

be added by forcing it through hand screw filler, or by means

a valve in the
of a portable

battery pump clamped to the side of the trail and connected through the trunnions to the interior of the cradle.

The

recoil

mechanism

is

housed inside of the cradle, through which

are bored an upper and lower cylinder, filled with Oleonapthe, able to communicate together by means of a passage provided for that

purpose.
piston)
is

The

front part of the upper cylinder (in front of the permitted to communicate freely with the air through a

87

88

if
1

Mil?

89
plug, but the forward end of the lower cylinder is closed and contains compressed air at approximately 150 kilograms per square

centimeter (1,833.5 pounds per square inch). In the upper cylinder a piston is permitted to move, the piston The lower cylinder is rod, however, being secured to the gun. fitted with a pipe, at the end of which is a circular ring, this pipe being screwed in the rear part of the cylinder where the valves are housed. A diaphragm equipped with a hollow rod, also a floating piston fitted with a small rod, a/re incorporated in the low er cylinder. During recoil the piston of the upper cylinder compresses the
r

liquid, forcing it to pass through various valves, also openings formed between the pipe and the hollow rod of the diaphragm. The passing of the liquid through these different openings constitutes the

LEFT SIDE VIEW OF CARRIAGE.
braking, in so moving, the liquid opens the valves (which are widely opened at the beginning of the recoil and gradually close in proportion to the decrease of the speed of the recoil). At the same time, the air in the lower cylinder is compressed by the action of the
liquid

recoil,

on the diaphragm. To return to battery at the end of the the compressed air forces the diaphragm back. The liquid thus compressed acts directly on ,the upper cylinder piston, causing
to return to its initial position.

it

The interior of the recoil mechanism was maintained confidential by the French Government before and during the war, and when its manufacture was taken over by the Ordnance Department, agreement was made to continue the secrecy of these parts. Very fine adjustments are made when the parts are assembled, and consequently no repairs or adjustments are permitted to be made in the field. The complete recoil mechanism must be sent to special

90
repair depots. the operating

The

recoil

mechanism

will function properly

without

mechanism. personnel understanding The angle of site mechanism consists of a handwheel and gears, and provides for elevating or depressing a rocker 13 degrees with The rocker fits around the trunnions and reference to the trail. has a segment of a gear which meshes with the elevating pinion. To the rocker is secured an elevating screw and nut which connects with the cradle. In setting the angle of site, the rocker is set in motion, thereby moving the cradle and gun. The range scale mechanism which operates the elevating screw provides an elevation of 12 degrees to give the correct range and is
the
interior

movement of the cradle in reference to the rocker. The circular scale graduated in meters indicating the range, is mounted on the side of the cradle and through gearing is connected
obtained by

A range rack is connected to the rocker graduated in meters. On carriages made in America an extra strip is placed alongside the range rack and is graduated in mils. The range scales are graduated up to 5,500 meters, but greater ranges can be obtained by burying the trail, and thus giving higher angles of elevation. Interference of the breech against the trail, however, limits the total possible elevation obtainable by combination of the elevation due to the angle of site
to the elevating screw.

arm which

is

also

and due

to range to 19 degrees.

geared nut, held inside is threaded with of this nut forces the a coarse rectangular thread. Movement carriage to the right or left, pivoting around the spade, one wheel advancing and the other backing up. Traverse is about three
this carriage axle traverse is used.

On

A

of the axle housing, rotates around the axle which

degrees right and three degrees left. combination road brake and firing support is hung around the axle, permitting the application of brake shoes against the tires of the wheels when traveling, and the lowering of the framework to

A

the ground and mounting the wheels thereon, for firing. This last operation is called abatage, the three steps being indicated in the

following figures:

POSITION

I

POSITION Z

POSITION 3

ABATAGE
Wooden

POSITION

wheels, 1,334 millimeters (52.5 inches) diameter, are used,

and have steel tires 3.5 inches wide. These wheels are interchangeable with the French limber wheels, but not with the American
limber or caissons for the 75-millimeter gun carriages.

91

92

93

The customary
under
fire.

shield

and apron protects the gunners when
is

The angle

of site

mechanism

also
is

of sight, the angle of sight, which is done by the angle of sight handwheel. The sight, model of 1901 (French), includes the collimating sight, angle of site level, and angle of site scale. It is mounted on the left side of the rocker, at the trunnions. It has no telescopic features
%

because the range setting

called the independent line independent of the setting of

and, therefore, its range is limited. An auxiliary angle of site level furnished to replace the regular level and gives an additional 200 mils for use in the hilly or mountainous country. Fixed ammunition is used in this 75-millimeter field gun and is
is

either common shrapnel or common steel shell. Shrapnel rounds are issued with the projectiles filled and fuzed; the shell rounds are issued filled but not fuzed, and contain an adapter with booster charge.

made up with

16 pounds, fuzed; one round are the cartridge case, with primer; the powder charge; projectile; and fuze, in shrapnel; and adapter and booster in the shell.
shell,

The

projectiles average in weight: Shrapnel, 12.3 pounds, fuzed. The components of

gun caisson limber, model of 1918. and store wagon, model ol 1917. Battery Forge limber, model of 1902M1. Store limber,. model of 1902M.1. 1 Battery reel, model of 1917. Reel, model of 1909M1. Cart, model of 1918. The gun and carriage are of the French design, and of both French and American manufacture. The accompanying vehicles are all of American design and manufacture.
75-millimeter
1 1
1

For horse

batteries the battery reel,
cart,

model

of 1917, is issued.

of 1909

Ml, with the

model

of 1918, is issued in lieu of

For motorized batteries, the the battery reel, model of 1917.

reel,

model

75-MILLIMETER GUN MATERIEL, MODEL OF
(BRITISH).
The known

1917

75-millimeter gun, model of 1917 (British), was originally as the 18-pounder, but was modified by adapting it to the 75-millimeter caliber materiel. This weapon is equipped with custrail;

tomary unit

the interference of the

trail

with the breech limits

the gun elevation. into the V formed
listic

With the split trail, the breech can pass down by separating the two sections of the trail. The

theoretical elevation for obtaining

maximum

conditions

is

45

from the horizontal, and

range under ideal balis actuallv some few

FRONT VIEW OF CARRIAGE.
this. Increased range is sometimes obtained with guns whose normal elevation is limited by setting the axles or wheels on raised surfaces, or by sinking the trail below the level of the wheels, for the purpose of pointing the gun at an elevation higher than the mechanical arrangement of the carriage permits. This is, however, a subterfuge, limited in its practical application. The American model 1916 split-trail carriage permits great elevation within the mechanism of the carriage and likewise a wide traverse without changing the position of the trail. The recoil mechanism on the 1916 model was adapted to the higher permissible elevation of the gun, and was supplied with a variable recoil, auto-

degrees less than

field

matically adjusted to different elevations.
(94)

The

ability to outrange

18322820

7

96

97
is an attainment constantly being sought, and therefore elevation and reduction of resistance of the projectile passing high obtain the through air are the means through which it was hoped to increased range desired. Likewise, a wide horizontal arc of fire,

the

enemy

without resetting of the trail and consequent resetting of the sightand saver of time. ing devices, is a great convenience As compared with the British model 1917, the American 3-inch model of 1902 carriage permits of a maximum angle of elevation of 15, depression of 5, and traverse of 142 mils, while the British

REAR VIEW OF CARRIAGE.
tion of 19, depression 10, and traverse 106 mils. The American model 1916 carriage allows a total vertical movement of from 53 elevation to 7 depression, and a traverse of 800 mils (an artillery mil equals the angle of -6-4W f a circumference). The American model 1902 carriages are arranged with an hydro-spring recoil mechanism, and so is the British model 1917 and the American model 1916. The French model 1897 carriage is equipped with an hydropneumatic recoil mechanism. The basic difference of the recuperator or recoil mechanism of the French model 1897 gun, as compared with the British model and the American model, lies in the fact that the French model involved the principle of oil and compressed air for absorbing the recoil of the gun

98
it to battery or firing position, and is practically selfcontained in one large heat-treated steel forging, with a system of In the British and finely fitted surfaces and adjustment valves.

and returning

American model
compressed
steel tubing.
air,

recoil mechanism, oil and steel springs, instead of are employed, with a combination of pistons and

A reference may

also

be made relative to the desirability of single

or unit trails as compared with the split trail. The latter allows of greater traverse, but as a new objective makes necessary a resetting of the trail, the change in setting requires much more time than with

the unit trail. The split trail is heavier and the equalizing mechanism, necessary to the proper distribution of recoil shock to both trail sections, establishes a relative movement between the two trail sections, with the result that the split trail can be set up less quickly

layers of steel wire, jacket, and breech ring. from the rear end of the chamber to the muzzle.
tion of the tube are

The tube extends

Over the rear por15 layers of steel wire. The jacket is fitted over the exterior of the tube and wire, and is secured longitu-

wound

dinally by corresponding shoulders and the breech ring, which is screwed over the jacket at the rear and secured by a set screw. The breech ring is prepared for the reception of the breech mechanism, and is provided on the upper side with a lug for the attachment of the hydraulic buffer. Longitudinal projections on each side of the

jacket form guides for the gun when in the cradle of the carriage. A plane for a clinometer is prepared on the upper surface of the breech Vertical and horizontal axis lines are cut on the face of the ring.

muzzle for use in verifying the adjustments of the sight. The breech block is of the interrupted screw type having two threaded and two slotted sectors. The breech recess of the gun is slotted and threaded to correspond with the threads on the block and the latter is screwed to a cylindrical section, or carrier, which is hinged
to the right side of the breech.
is

Hinged

to the rear face of the carrier

lever, provided with bevel teeth which engage with correteeth on the rear face of the breech block, so arranged that sponding

a

hand

when

the lever is pulled to the right, the first movement of the lever unlocks the breech block, and on continuing the motion the block and carrier are swung into the loading position. The breech is opened by the cannoneer on the right seat pulling the hand lever toward him. The extractor, hinged to the right side of the breech, is automatically actuated in opening the breech, thus ejecting the

empty

cartridge case.
is
is

The firing mechanism
before the breechblock

so arranged that the gun can not be fired home and the hand lever locked and is

lever

as a continuous-pull mechanism. By means of the firing on the left side of the gun, operated by the gunner, the firing pin which seats in an axially bored hole in the breechblock, is cocked and fired by one continuous backward motion of the lever. The carriage has a tubular steel trail and axle, the rear end of the trail being fitted with a spade, lifting handles, trail eye, and traversing lever. The top carriage is provided with bearings, by means of which it is pivoted on the axle for traversing. Bearings are provided at the top to receive the cradle trunnions on which the cradle pivots.

known

Longitudinal recesses are cut in the inner surface of the lower portion of the cradle for the reception of the guides on the jacket of the gun. A seat is provided on the left side of the trail for the gunner who sets the sights and fires the gun, and one on the right for a cannoneer who sets the range and operates the breech.

101

102
TJio
''Mi&ooTriar^ tojJ
1

fc,n*J'

main

shields

and the apron are provided
upper porinner and outer, of (running-out) springs, these
sets,

for the protection of the personnel against gun fire. The recoil cylinder is contained in the spring case in the

tion of the cradle

and

is

surrounded by two
counterrecoil

four sections

each,

of

being held under initial compression between an external flange on the front end of the recoil cylinder and an internal flange at the rear

end of the outer spring case. The cylinder is attached and secured to the rear end of the gun by two nuts, while the piston rod with piston, which fits inside of the cylinder, is secured to the forward "end of the spring case. The piston rod is bored out for the reception of the counter recoil buffer which is secured in the rear end of the cylinder. Upon being fired the gun recoils, carrying with it the recoil cylinder. The oil is forced to pass from in front of the stationary piston to the rear through grooves of graduated depth which set up an hydraulic resistance, thus checking the energy and bringing the gun to rest. In recoiling, the gun further compresses the two sets of springs which, after the gun has reached its maximum recoil, cause it to return to battery. The counter recoil buffer displaces the liquid in the rear end of the piston rod, the liquid being forced to escape
over the tapered flats, thus resulting in the gun returning to battery without shock. A gravity tank is bolted to the front end of the recoil mechanism, which insures the cylinder being constantly filled, and is protected

from gun fire by a shield. The angle of sight level is carried on a bracket riveted to the underside of the rocking bar at the rear end and is adjusted by a leveling screw to which is attached a micrometer disc for setting off the
angle of sight.

The range indicator is fitted to the right side close to the handwheel and consists of a meter scale ring graduated on its face in hundreds

mechanism allows an elevation

of meters, the periphery of the ring being graduated in mils. of 16 and depression of 5.

The

The elevating gear is divided into two portions, upper and lower, and so arranged that the gun may be elevated or depressed without
altering the line of sight.

The traversing gear is pivoted to a bracket fastened to the trail at the rear end of the top carriage, and is operated by a handwheel extending out to the left side by means of which the gun may be
traversed 72 mils right or left from center. scale strip and pointer indicate the angle of traverse. Wooden wheels, 56 inches in diameter, are used, having steel tires 3 inches in width. Drag washers free to rotate about the hubs are

A

secured by the dust cars.

103

104

105 The tire brake is for use in traveling, and is always used when firing. Brake arms are pivoted at one end to a bracket on the trail and have at their other end a cast-iron brake shoe which acts upon the tire of the wheel. The braking action is adjustable and brakes are operated by a lever having an eccentric link at its end. The sights used are the rocking-bar sight and panoramic sight, model of 1917, which are located on the left side of the carriage. Fixed ammunition is used in this 75-millimeter field gun and is

made up

of either

common

shrapnel or

common

steel shell.

Shrap-

nel rounds are issued with the projectiles filled and fuzed; the shells rounds are issued filled but not fuzed, and contain an adapter with

booster charge.
shell

pounds fuzed; round are the cartridge case with primer, powder charge, projectile, and fuze in shrapnel, and adapter and booster in shell.
75-MILLIMETER GUN MATERIEL, MODEL OF
1917 (BRITISH). is

The

projectiles average in weight; shrapnel, 16 12.3 pounds fuzed. The components of one

75 millimeter giving interchangeability with French ammunition. All of this materiel used by the American Army was manufactured in the United States. The gun carriage limber, model of 1917, is of
British design.
1

Either one of the above limbers

may

be issued.

75-MILLIMETER GUN CARRIAGE LIMBER, MODEL OF
1917 (BRITISH).

The standard British limber carries cartridges horizontally, but not arranged with compartments or diaphragms. The American product of the British limber is superior to the standard British vehicle in that diaphragms are included in the ammunition chests. The limbers are, however, fitted with wooden poles, which are more liable to breakage than steel poles; they have single draft hooks, instead of double trees for equalizing the pull on the braces; the pintle latch is not so effective as the American, nor the ammunition chest doors so well suited to their purpose; and they are not adapted to the American harness, as the distance from the neck yoke to the draft hook is 6-inches shorter than in the American design and our harness can not be so readilv connected to the neck voke.
is

FRONT VIEW OF LIMBER.
Weights, dimensions,
etc.

Weight, complete, empty

pounds.

.

1,

016
114

and equipment carried do of ammunition carried do .... do Weight, completely equipped and loaded Weight of gun, carriage and limber, completely equipped with 21 rounds of ammunition pounds. inches Diameter of wheels Weight Weight
of tools
.
. .

516
1,

.

646
591 56 60 70

.

4.

.

.

Width

of track

do. ...

Turning angle with carriage

degrees

.

.

consisting of

gun carriage limber is constructed of a frame two middle and two outer rails connected at the front and center by a bar and braces and surmounted by an ammunition
British design of
(106)

The

chest of steel.

107

K

I
s
VJ

I

108

fc

109
at the rear and is fitted with perforated diaphragms rounds of fixed ammunition and a compartment in the center holding two wooden trays for small stores. The pole is of wood, protected at the front end by steel wrapping plates and fitted with a neck yoke for use with breast collar harness.
for carrying 24

The chest opens

REAR VIEW OF LIMBER.

The

axle

is

a seamless steel tube fixed to the rails

by

flanges,

and

the wheels are the

same

as those used

on the gun

carriage.

used only in connection with the 75-millimeter gun carriage, model of 1917 (British). The 75-millimeter gun carriage limber, model of 1918 (American) a description of which may be found on page 110, can be used as an
is

This limber

alternate for this vehicle.

75-MILLIMETER GUN CARRIAGE LIMBER, MODEL

CF
The limber

1918.

is of American design, and is of metal throughout, the spokes and felloes of the wheels. The frame consists excepting The middle rail is in the form of of a middle rail and two side rails.

a split cylinder, one-half passing below and the other half above the axle, uniting in front to form a seat for the pole and in the rear to form a seat for the pintle-bearing guide. An automatic pole support, described on page 160, is provided.

The ammunition chest is a rectangular steel box, having a door at the rear hinged at the bottom, and swinging downward to an approximately horizontal position. Three perforated diaphragms within the chest support 18 rounds of fixed ammunition and 3 tubular oil cans. The axle is of forged steel, made in one piece. The standard 56-inch wheels are used. See page 158. This limber is used in connection with American, British, and
French 75-millimeter materiel.
Weights, dimensions,
etc.

The caisson consists of a steel chest carried on wheels and axle by means of a spring support. This support consists of helical springs held by suitable axle and chest brackets at each end of the chest. The Belleville springs absorb the shock of rebound.

FRONT VIEW OF CAISSON.

ammunition arranged in 5 horizontal Protection from small-arms fire is provided by the front door, rear plate, and apron, which are made of armor plate. The chest provides seats for three cannoneers, and is equipped with A rack is provided fastenings for carrying a full complement of tools. at the back of the chest for carrying fuze boxes. On the front left
chest carries 70 rounds of

The

rows

of 14 each.

fastened the fuze setter. equipped with a short pole and lunette combined with a pole prop. On the rear the standard pintle is provided.
side of the chest
is

The

caisson

is

(113)

114

gfe

g^ia

i

I

115
Standard 56-inch wheels are used and band brakes are provided. See page 158.

The gun caisson limber is practically the same as the gun carriage limber, model of 1918, except that the chest is larger and carries more ammunition. Each diaphragm is perforated with 39 flanged holes, which accommodate 36 rounds of ammunition, and three
tubular oil cans. This limber is used in connection with the American, British, and French 75-millimeter materiel.

The needs of the fighting army received first attention, but a large number of troops in the training areas and camps required materiel
for use in their preliminary instructions; thus 154 batteries of 3 -inch model 1902, materiel were distributed for training purposes in the

United States which were considered substitutes for the 75-millimeter
materiel.

The 3-inch field gun, American model 1902-1904-1905, is equipped with a breechblock of the interrupted-screw type. The breech mechanism consists of a handle pivoted vertically to provide horizontal movement of the handle to the right to open the breechblock. In opening, the mechanism performs two functions: Revolves the breechblock, releasing it from the threads, and then swings the block open. At the same time the cartridge case is ejected from the gun. In closing, the threaded movement firmly seats the cartridge in the powder chamber, and the threads withstand the backward thrust
of the
is of the hydro-spring type, with the housing attached to the carriage, and located underneath the cannon. The firing mechanism, in the latest design, is operated either by a lanyard attached to the trigger, or by means of a firing handle on the cradle, and is of the continuous-pull type. \Yhen the breechblock is unlocked the gun can not be fired.

Weight of gun and carriage fully equipped Weight at end of trail, carriage limbered Diameter of wheels
,

do do
inches
.

2,

115
.

56

Width

of track

Length of recoil of gun on carriage Height of axis of gun Height of line of peep sight Length of peep-sight radius

do do do do do
degrees
.

60

45
40.

875
75
15
5

44. 9
36.
.

Maximum Maximum
Amount
Rounds
of

angle of elevation angle of depression

do
mils
.

of traverse of

gun and carriage ammunition carried on carriage

.

140
4

3-INCH GUNS,

MODELS OF

1902, 1904, 1902.

AND

1905,

AND CARRIAGE MODEL

OF

are of three models, 1902, 1904, and 1905, and are pracsame except that the latter two models differ from the 1902 model in breech mechanism and the 1905 model is 50 pounds
tically the

The guns

up of nickel steel and consists of a tube, the rear portion of which is enveloped by a jacket which also projects beyond the rear end forming a recess for the breech block. locking hoop is shrunk on the tube and the forward end of the jacket to secure the latter to the tube. The front clip is a short hoop shrunk on the tube near the forward end which guides the gun in recoil.

lighter in weight. The gun is built

A

The breechblock on

all

three models

is

of the interrupted-screw

type, and rotates in the block carrier which is hinged to the rear end of -the tube on the right, side. The block of the 1902 model has

two threaded and two slotted sectors and the block of the 1904 and 1905 models which have identical breech mechanisms, has four threaded and four slotted sectors. The breechblock is operated

c
<3

I

(122)

.

ill
"

!

!

1

124
by a lever pivoted to a lug on the block carrier which has at its outer end a handle and at its pivot end, a segment of a bevel gear, meshing with a corresponding segment on the rear face of the block. On pulling the handle to the right, the first 117 rotates the block until
the threaded sectors are disengaged. A further movement of 90 swings the block and carrier on its hinge until free of the bore. The firing pin is eccentrically "located in a recess in the block, when the breech is open. As the breech is closed the pin is automatically moved to one side until it is in alignment with the axis of the bore and primer of the cartridge case. This is a safety feature which prevents the accidental discharge of a round before the breech has been fully closed.

The carriage
trail is

is known as model of 1902. A tapering box-shaped secured to brackets around the axle and has at its rear end a

float. Two compartments are provided in the trail, one and one for the rear sight. A seat is riveted to each side of the trail, one on the left for the gunner, and one on the right for a cannoneer. In front of the compartments are two cross transoms which form a support for the elevating mechanism. The cradle has riveted to its underside a pintle which seats in a pintle socket secured to the axle, by means of which the cradle and gun is rotated. The top and main shield and an apron are provided for the protection of the personnel from gun fire. The recoil mechanism is of the hydro-spring type. The recoil cylinder is fastened to the gun lug and therefore recoils with the gun.

spade and
for tools

The piston
during

recoil.

rod, "being secured to the cradle head, remains stationary Throttling during recoil is obtained by the use of

three throttling bars, on the interior of the recoil cylinder, the piston having three slots cut in it to correspond to the throttling bars. During recoil the piston is stationary and the hydroline oil in the cylinder is forced past the piston through the slots. As the throttling bars, due to their increasing size, gradually close the slots in the
piston, the gun is gradually brought to a stop. The counterrecoil mechanism consists of three nests of inner

and

outer springs which function to return the gun to battery and serve to partially check the recoil. The counterrecoil buffer consists of a rod secured in the end of the cylinder which enters the hollow tapered

end

when

of the piston rod, displacing the oil therein the gun returns to battery.

and preventing shock

The elevating mechanism is of the double-screw type, consisting of a screw pivoted to the rear end of the rocker, which is moved up or down by the rotation of a bevel gear threaded on its interior surface.
This bevel gear is rotated by a bevel pinion operated by a crank handle on either side of the trail

125

12G
Traversing is accomplished by means of a traversing shaft operated This shaft is by a handwheel on the left side of the carriage. threaded and passes through a nut which is pivoted to the cradle. The nut being secured to prevent its turning, swings the cradle in traverse, when the traversing mechanism is operated.

A

lock

is

provided for locking the cradle to the

trail in

order to

relieve the elevating and traversing strains during traveling.

mechanisms

of

any unnecessary

CARRIAGE AND LIMBER HAULED BY TRACTOR.
Seats are supported on the axle on each side of carriage in front of the shield for the cannoneers, when traveling. Foot rests are provided which also support the brake levers and ammunition carriers,
there being four of the latter which quickly if necessarv
.

make

it

possible to open fire

CARRIAGE AND LIMBER

IN

TRAVELING POSITION.

The brakes

are of the shoe type

and

may

be operated from either

in front or rear of the shield, in the former case in the latter case when in firing position.

when

traveling,

and

Standard 56-inch wheels are used.

for sighting line sights, a rear sight, a front sight, a

The instruments provided

See page 158. and laying the piece include panoramic site, and a range

quadran t. Three kinds of fixed ammunition are used in the 3-inch gun, models of 1902, 1904, and 1905, namely, common steel shell, common Each round is issued with shrapnel, and high explosive shrapnel.

127

1832282

128

129
projectiJes filled and fuzed. and the total weight of one

The weight of the projectile round is 18.75 pounds.
1902.

is

15

pounds

3-INCH

GUN MATERIEL, MODEL OF

This materiel includes the following: 3-inch field gun, model of 1902, 1902 or 1905 mounted on

principal parts are the wheels, axle, frame, ammunition chest, pole, doubletree, singletrees, and neck yoke. The wheels and wheel fastenings are the same as, and interchange-

The

The axle is hollow, of a single able with, those used on the carriage. piece of forged steel, the axle body being provided with lugs, to which the middle and side rails of the frame are riveted. The side rails are of channel shape, divided at the front, one branch being led forward and secured to the middle rail near the pole seat,

REAR VIEW OF LIMBER.
while the other branch is utilized as a foot-rest support. The foot rest is a perforated steel plate formed to shape and riveted to the middle and side rails in front of the ammunition chest. The rear

ends of the side rails project slightly beyond the chest to form steps for the use of the cannoneers in mounting. The frame consists of a middle and two side rails riveted to the axle lugs. The middle rail is in the form of a split cylinder, one-half passing below and the other half above the axle, which are joined in
front to form a seat for the pole

and

in rear to

form a seat

for the

The pintle bearing is of bronze, made in halves and pintle bearing. bored out to take the pintle shank. The pintle has a swiveling motion of 360 upon its shank, but is kept in its normal position by the spring
in the bearing.

The doubletree and singletrees are formed of flange steel. Two doubletree rods each from the ends of the doubletree to the tie-rod
(130)

131
clamps on the axle to which they are pinned. A pole prop is hinged end of the pole and when not in use it is secured by fastenunder the limber frame and the prop-chain button on the foot rest. ings
to the rear
steel

The ammunition chest is a rectangular steel box built up of sheet and riveted together. The chest door is hinged at the bottom and swings downward and to the rear to an approximately horizontal position, where it is held by two door chains, and is held in its closed
position

by

a shot bolt at each of the upper corners

and by a lock

in

the middle.
Inside of the chest the cartridges are supported by three vertical diaphragms, flanged all around and riveted to the body of the chest.

diaphragms is perforated with 39 flanged holes. Correholes in the middle and rear diaphragms are connected by sponding conical brass tubes, which are cut away on top to reduce weight. These connecting pieces support the front end of the cartridge case

Each

of the

and enable empty cases

to be carried.

The

rear end of the connecting

piece is turned over the rear face of the flange of the perforation in the rear diaphragm, and forms a stop for the rim of the cartridge

The chest door closes against the head of the case so that the Suitable finger clearances are cartridge is firmly held in position. cut in the flange of each cartridge hole in the rear diaphragm to enable the fingers to get a good hold on the rim of the case in withcase.

drawing

it

from the

chest.

Seats for three cannoneers are provided and the paulin issued with each limber serves as a seat cushion. Watering buckets are carried
in suitable
chest.

compartments provided for them between the seat and the At each end of the seat is a handrail which projects above the top of the chest. At the front a lantern and two picket ropes are carried. Brackets for carrying an ax, a shovel, and pole

prop are provided under the limber. All of the implements are secured in their brackets by leather straps, and held by strap fasteners provided for that purpose. With each limber are issued three oil

form of a cartridge and of a capacity of They are intended for hydroline, lubricating, and coal oil, and are to be carried inside the chest in the central vertical row of cartridge holes.
cans, each of the general

approximately two-thirds of a gallon.

Weights, dimensions,

etc.

Weight, complete, empty

Weight Weight

and equipment carried of ammunition carried Weight, completely equipped and loaded "Rounds of ammunition carried in limber chest Diameter of wheels
of tools

This caisson, with the exception of the spokes and felloes of the wheels is of metal throughout. The frame is diamond-shaped and composed of two channel section side rails riveted to lugs on the axle and meeting in front and rear
at the lunette

and

pintle, respectively.

FRONT VIEW OF CAISSON.

The ammunition chest is a rectangular steel box of flange steel containing three vertical diaphragms which support 70 rounds of ammunition. Caissons having serial numbers 1141 to 1284, inclusive,
have provisions
for

but 56 rounds.

is in the rear and hinged at the top, the door opening upward and held at each end by a prop. An apron of armor plate is hinged under the axle and may be secured in a horizontal position for traveling. A fuze-setter bracket is pivoted to the apron hinges on the right side of the carriage at the rear. t is raised and secured for traveling. The road brake is designed similar to that of the gun carriage, with all parts as far as possible being interchangeable. The standard 56-inch wheels are used.

consists of two side rails and a middle rail braced by and by the ammunition chest to which they are riveted. The chest is a rectangular flange steel box containing three vertical diaphragms supporting 70 rounds of ammunition. The door is hinged to the front of the chest, swings upward on its hinges and is held by a door prop on the left side. An apron of armor plate is hinged below the chest for the protectie rods,

tion of the personnel.

FRONT VIEW, SHOWING DOOR SWUNG UPWARD EXPOSING AMMUNITION.

Band brakes
riage,

are used similar to those on the

75-mm. gun

car-

model

Brakes one of the cannoneers seated on the chest.
Weights, dimensions,

of 1916, several parts of which are interchangeable. are applied by a hand lever on the right side, operated by

two side rails joined at the front to form a and projecting directly to the rear beyond

RE\R VIEW OF BATTERY WAGON.
chest is of wood and is bolted to the side rails. The interior divided into four compartments; the largest being accessible through a hinged lid at either end of the top. The other three com-

The

is

partments are in the lower rear portion of the chest, and are entered by a door at the rear end which opens downward. Of the three compartments, the right one is for the saddler's chest the left one for the carpenter's chest, and the middle one for the cleaning materials and small stores chest. In the larger compartment is carried the grindstone and frame; the jackscrew; and the packing chest containing spare breech mechanism. A chest for spare sights is furnished, which may be carried either in the battery or store wagon.
;

(138)

139
In rear of the axle and under the chest are carried three
of 5 gallons capacity each.
oil

cans

Fastenings are provided on either side of the chest for carrying the two spare wheels. The wheels used and carried are standard 56-inch. See page 158. This battery wagon is used only in connection with the 3-inch gun
materiel,

The battery wagon, model of 1902 MI, differs from the model of 1902 in the following respects: The chest with attachments is stronger, better braced, and attached in a better manner to the frame. The weight of the spare wheels is carried directly by the axle instead of at the top of the chest. The parts of the chest are bolted and screwed together so that they may be readily disassembled if necessary. The corners are not dovetailed but reinforced with corner irons inside and out. This battery wagon is used only in connection with the 3-inch gun
materiel,

model

of 1902.
Weights, dimensions,
etc.
:

Weight Weight

of
of

battery wagon, empty battery wagon, completely equipped and loaded
of

pounds
do

.

.

1.

444
947
56

2,
.

Diameter

wheels

inches.

Width

of track

Free height under wagon Turning angle with limber

do do
degrees.
.

60
24. 5

75

Weight (approximate)

at lunette, loaded

pounds.

.

112

STORE WAGON, MODEL OF

1902.

The store wagon is the same as the battery wagon, model of 1902, with the exception that the vise is omitted and a frame handle attached in its place, and the body has but a single compartment, with two doors on top. As on the battery wagon, the store wagon carries two spare wheels and three oilcans.

SIDE VIEW OF STORE WAGON.

The store wagon is intended primarily for carrying silch stores, spare parts, and materials as can be carried in the battery wagon and,
in addition,

such stores as

may

Tire brakes are used operated of the body.

be designated by proper authority. by a hand lever on the right side
are

store wagon, model of 1902 MI, is the same as the battery wagon, model of 1902 MI, with the exception of the differences as

noted in the description of the battery store wagon, model of 1902.

For detailed description and table
see page 139.

of weights, dimensions, etc.,

142

FORGE LIMBER MODEL OF
The frame
of the 3-inch
of the forge limber
is

1902.

gun limber, model

of 1902.

identical in all its parts with that It consists of a middle and

two side rails, the middle rail being in the form of a split cylinder, one half passing below and the other half above the axle, uniting in
front to

form a seat for the pole and in the rear to form a seat for the pintle bearing guide. The chest is a rectangular flange-steel box having a lid hinged along the front edge of the chest body. The lid is flanged all around,

1

TOP VIEW SHOWING INTERIOR OF FORGE LIMBER.
fitting

bolts

over the body of the chest to make it water-tight, Shot of the chest secure the lid when closed. The interior of the chest is divided into five compartments by The middle compartment, which is four vertical steel partitions. the largest, is fitted to take the field forge, the anvil, and several small tools, the next compartment on either side carries horseshoes and horseshoe nails, and the end compartments are fitted with

on the rear face

fastenings -for carrying smiths'

and machinists'
(143)

tools.

A

tubular

oil

18322820

10

144

145
carried under each end of the chest, and various implements are secured to the chest by straps provided for that purpose.

The forge limber, model of 1902 MI, is identical with .the 1902 model, with the exception that the 1902 MI model has an automatic pole support, which is described on page 160. The forge limber is used in connection with the American, British,
and French 75-millimeter materiel, and the 3-inch gun materiel, model of 1902. A detailed description and table of weights and dimensions is given in a preceding article on forge limber, model of 1902, page 143.

STORE LIMBER, MODEL OF

1902.

The store limber is practically the same as the forge limber, model of 1902, except that the chest is fitted with compartments for carrying fire-control equipment, some of the compartments being padded
to protect the contents from injury. For description and table of weights
article

and dimensions, see preceding

on forge limber, model

of 1902.

TOP VIEW SHOWING INTERIOR OF STORE LIMBER.

STORE LIMBER, MODEL OF
The
store limber,

1902

Ml.

model

of 1902

Ml,

is

identically the

same

as the

store limber,

model

of 1902,

with the exception that

it is

fitted

with

an automatic pole support, description of which will be found on page 160. For description and table of weights and dimensions, see preceding article on forge limber, model of 1902.
STORE LIMBER, MODEL OF
1902 Ml.

The limber is used in connection with the American, British, and French 75-millimeter materiel, and the 3-inch gun materiel, model
of 1902.
(146)

BATTERY AND STORE WAGON, MODEL OF

1917.

The battery and store wagon is made of metal throughout, with the exception of the spokes and felloes of the wheels. The frame is built up of two channel section side rails connected at the rear and intermediate points by similar channels. The side channels are bent
inward near the front, meeting and forming a seat in which the

REAR RIGHT SIDE VIEW OF BATTERY AND STORE WAGON.
lunette bracket
is

riveted.

At the rear

of the

frame is a compartment

for carrying recuperator, lubricating, and coal oil cans. The chest is divided into compartments for carrying various articles

battery equipment. The top compartments have horizontally hinged lids and the lower compartments in front and rear have vertical swing doors. Fastenings are provided on each side of the
of

The battery and store wagons are identical, except that the battery wagon carries a vise on the front end of the frame and a crow bar bracket below the frame on the right side, and the store wagon contains packing strips and accessories for carrying a grindstone in the
r

upper rear compartment. Standard 56-inch wheels are used. See page 158. The battery and store wagon is used in connection with the American, British, and French 75-millimeter materiel, and with the 3-inch gun materiel, model of 1902.
Weights, dimensions,
etc.

BATTERY REEL, MODEL OF
The battery reel, model of is drawn by 4 horses.

1917.

which

1917, is a single two-wheeled vehicle It is designed to carry, lay, and recover 4 miles of insulated cable, and in addition carries 2 steel

chests containing fire-control instruments.

The frame is composed of two side rails connected by cross members and diagonal braces. Near the front, the side rails converge and are Axle brackets are riveted to the side rails, riveted to the pole socket.

LEFT SIDE VIEW OF BATTERY REEL.

which are mounted the axle arms for the wheels and the drum on which the cable drum rotates. On -each side of the drum are supports which are joined across the top by a seat for two men. Across the frame in front of the drum is secured an instrument chest divided into two compartments with separate hinged lids, the lids forming foot rests for the personnel on the seat. Across the frame in rear of the drum a large steel chest is supported on springs. It has a lid hinged at the front and provided with guide rollers for the cable at its rear. The larger fire-control instruments are carried in this chest in specially designed comin

shaft

partments. On the right side of the
plotting board
is

drum

is

secured a steel case in which a

carried.
(150)

151

At

either

end
a

of the

drum

is

a sliding leather-faced cone

which

is

controlled

by

hand
is

When

either cone
is

lever at the left end of the operator's seat. engaged, the other is disengaged. The cone on

connected directly to a gear train driven by a gear attached to the wheel hub, and when er gaged causes the drum to revolve. As the brake cone on the right is engaged the clutch cone is thrown out of engagement. The wire, when being laid out, leaves from the top of the drum, passing between the guide rollers attached to the
the left
rear chest.

The
is

cart, model of 1918, together with the reel, model of 1909MI, issued in lieu of the battery reel, model of 1917, for motorized
Weights, dimensions,
etc.

model of 1909 Ml, is a two-wheeled vehicle designed to and recover 8 miles of insulated cable. It has interchangeable pole connections which enable it to be adapted to either horse or motor traction. The frame is composed of special shaped pressed steel members connected by gusset plates and reinforce pieces, the pole socket at the front, automatic pole support, a pintle at the rear, and the assemreel,

cany,

lay,

bled axle.

REAR VIEW OF REEL.

s

Two drums, which carry the cable are mounted end to end on an axle which rests in the upper ends of the axle brackets. In order to the wire, the drums are disengaged from the clutch, permitting lay them to revolve free upon their axes, but controlled by the braking
action of the

drum

latch and

drum brake

or the friction clutch

when

applied for that purpose. To' recover the cable or wind it on the drums, the clutch in the right drum is applied, and the drum made to
revolve, wheel.

clutch

by means of the chain driving gear attached to the right The left drum is driven by the right drum through a pin which is operated by a handle in the left outer end of the left
(152)

drum.

153

154

An

operator's seat

is

secured to the right rear corner of the frame,

and the controls placed within easy reach. The clutch connecting the drum driving gear and the right drum is located in a recess in the right drum head and operated by a handwheel at the upper end of a shaft mounted on the right axle bracket. A lever on 'the right side near the seat operates the drum latch for locking the right drum, and through the pin clutch, the left drum

when they are at rest. A leather faced brake shoe attached to the drum latch lever may be brought against the flanged rim of the right drum end plate to act as a brake. A brake shoe controlled by a foot lever near the operator's seat may be brought to bear against the flanged rim of the left drum end
plate.

FRONT VIEW OF REEL.

Wooden rollers are placed under the frame so that the wire will be laid out or recovered without injury to it. A tool box with lid opening on top is secured to the right of the pole bracket in the space between the side rail and front cross rail. The reel, model of 1909 Ml, together with the cart, model of 1918, is issued in lieu of the battery reel, model of 1917, for motorized
batteries.
Weights, dimensions,
etc.
:

The cart is a two-wheeled vehicle made of metal throughout, with the exception of the spokes and felloes of the wheels and the packing

%

VIEW SHOWING REEL AND CART, LIMBERED.

within the chest. It is designed to carry part of the fire-control equipment for the organization to which it is issued.

REAR VIEW OF CART.

The frame
brackets,

consists of a middle rail,

all of

two side rails, and two axle which support the chest. Tne forward end of the
(155)

156

157
middle
rail is fitted

with a lunette and the rear end with a pintle.

Spiral springs are interposed between the side rails and axle brackets to absorb the shocks when traveling. In connection with the axle

brackets, Belleville springs are used to take up rebound. The chest is made up of flange steel plates riveted together and fitted with doors, lock bars and packing devices, the interior being
;

divided into 17 compartments of different sizes. The chest is also furnished with fixtures on the exterior for attaching an observation tower.

band type and are operated from the operator's seat on top of the chest by means of a brake lever on the right side. This cart, together with the reel, model of 1909M1, is issued in lieu of the battery reel, model of 1917, for motorized batteries.
are of the contracting

THE 56-INCH WHEEL.
All carriages and accompanying vehicles of the 3-inch and 75millimeter materiel, of American design, are equipped with standard 56-inch wheels, which are interchangeable for all vehicles of these
materiels.

The wheel

is

in diameter, with 3-inch tires. is provided so that the wheel

a modified form of the Archibald pattern, 56 inches The tires are of steel. An oil valve

can be oiled without removing

it

SIDE VIEW OF WHEEL.

The wheel fastening consists of a bronze yoke fitting in the outer end of the axle arm and is accessible when the hub cap is removed.

THE

57

BY

3.5

INCH WHEEL.

In place of the above 56-inch wheel a 57 by 3.5 inch wheel may be used. It is similar in design to the 56-inch wheel, but is fitted with solid rubber tires. Like the 56-inch wheel it is interchangeable on all vehicles of the
3-inch and 75-millimeter materiel.
(158)

REEL,
One
phone
wire.

MODEL OF

1917,

FOR CAISSONS.

wire.

caisson in every battery is provided with a hand reel for teleIt is riveted to the top of the caisson and contains 1

mile of field wire so arranged that the current goes through all the Terminals are provided for the connection of the instruments.

REEL FOR CAISSON, MODEL OF

1917,

MOUNTED ON A

CAISSON.

model of 1917, is a hand-operated reel for the and handling of telephone wires. transportation The frame is built up of two-flanged steel ends and two sides, riveted together with four angle-iron corner reinforces and riveted to the top of the chest. The reel is built up of two steel spool flanges mounted on a shaft, a spool riveted to the right flange and a basswood spool hub mounted between the spool flanges. The spool may be operated from either side. The crank on the right side is mounted on the shaft, and when not in use it can be removed and placed in its provided receptacle. The crank on the left side is connected with the spool through an 18 to 40 gear reduction. The crank shaft is fitted with a driving gear which meshes with a pinion 18322820 11 (159)
reel for caisson,

The

160
on the shaft of the spool. Chains are provided on either end of the frame for locking the cranks when not in use. The reel is also fitted with a brake for controlling the speed of rotation when allowing wire to run out. The brake lever is pivoted on the brake-lever pin, and operated by a thong attached to the lower

REEL FOR CAISSON, MODEL OF

1917.

lever. By pulling the thong the upper end of the lever is to drag on the inside of the rim of the left spool flange. brake-release spring, attached to the upper end of the lever, and a lug

end of the

made

A

on the

left

shaft bearing, keeps the brake open

when not

in use.

THE AUTOMATIC POLE SUPPORT.
Late designs of limbers for 75-millimeter and 3-inch gun materiel are fitted with an automatic pole support. The pintle hook has a lug formed on its lower side, which projects backward and bears against the lower side of the lunette on the drawn vehicle, thus preventing the vertical rotation of the pintle.
PIMTU BEMl.n* 6UIDC'.

,

SICE*

I

,FlNTlE KAHIN6

SECTIONAL DIAGRAM OF POLE SUPPORT.
pintle bearing is pivoted by trunnion bolts permitting rotation in the vertical plane. spring rod is pinned to a lug on the top

The

A

carries the pole supporting spring. This spring is held between a collar on the rod and the pintle bearing guide so that when the weight of the pole on the coupled vehicle is put on the

of this bearing

and

pintle it tends to compress the spring until the load

is

supported by

it.

On
when

the pintle bearing bolt is another spring, which is compressed the pintle is drawn back, thus relieving the shock of starting.

4.7-INCH

GUN MATERIEL, MODEL OF

1906.

The 4. 7-inch, model of 1906, is a mobile field gun, designed to fire shrapnel or shell at greater ranges than the 75-millimeter guns. In order to increase the range, a 45-pound shell is provided to replace the old type 60-pound shell. The former projectile gives considerably higher muzzle velocity and longer range than the 60-pound projectile.

The

life

of the

gun before

relining

is

approximately 5,000

rounds.

seconds

Using the 60-pound shrapnel, a muzzle velocity of 1,700 footis obtained, with a maximum range of 7,550 yards (6,903 meters) at an elevation of -15. With the 45-pound shell, with a muzzle velocity of 2,050 foot-seconds, a maximum range of 8,700 vards (7,900 meters) at an elevation of 15, under normal conditions.

VIEW SHOWING CARRIAGE AND LIMBER IN TRAVELING POSITION.

gun is mounted on a carriage of the long-recoil which the gun is permitted a sufficient length of recoil on the carriage to render the latter practically stationary under firing stresses. The gun, in recoil, is controlled by two spring cylinders, and a hydraulic cylinder, which is filled with 25J pints of oil. In recoil, the oil in the hydraulic cylinder is forced from one side of the piston The
4.7 inch field

type, in

The area of these ports are the resistance which the liquid offers, plus the resistance of the springs, such that the wheels will not jump from the
to the other

through small portholes.

calculated to

make

ground when the gun recoils. In counterrecoil the oil is forced back through these small ports with the result that the return of the gun into battery is so eased and regulated that shock and consequent derangement of the aim is almost eliminated. To properly return
the gun. to battery at high angles of elevation, the springs are assembled with an initial compression of approximately 1,500 pounds in

each cylinder.
061)

162

163

164
equipped with a single trail, composed of two pressed anchored in the ground by a spade when in action. When traveling, the trail is supported by the carriage limber which may be drawn by either a truck or tractor. On account of the single trail the maximum elevation of the gun, without digging in the trail,
carriage
is

Tko

steel flasks,

and

is

is

only 15. The allowable transverse movement is 140 mils, or about 8. The motorized equipment of each gun carriage, as indicated below,

consists of a carriage limber,

and three

which supports the trail when traveling, which carry ammunition. caissons, 4.7-inch gun and carriage, model of 1906. 4.7-inch gun carriage limber, model of 1905. 4.7-inch gun caisson, model of 1916 or 1917. The above materiel is entirely of American design and manufacture.

LEFT FRONT VIEW OF CARRIAGE EQUIPPED WITH BAND BRAKES.
Weights, dimensions,

and

ballistics.

Weight

of

gun
,

pounds.
..inches.

.

2.

688

Total length

.

134. 927

Rifling Right hand, 1 turn in 50 calibers at origin to 1 turn in 25 calibers at 14.9 inches from muzzle, thence uniform.

Maximum angle of elevation (gun or carriage) Maximum angle of depression (gun or carriage) Amount of traverse
Height
of line of sight

15
5

do
mils...

140(7.8)
53.

inches.

.

92

1G5

166
4.7-INCH

GUN AND CARRIAGE, MODEL OF

1906.

The gun is of the built-up type, and consists of a tube, jacket, locking hoop, and clip. The jacket covers the rear half of the tube, and The projects beyond the tube at the rear to form the breech recess.

FRONT VIEW OF CARRIAGE EQUIPPED WITH TIRE BRAKES.
jacket is equipped with a recoil lug on the underside for connecting the recoil cylinder. The clip is a short hoop near the muzzle and is
fitted

with guides to guide the gun in the cradle on

recoil.

TRIGGER rORK

CXTRKTOR
rIH6 HHNOLC
TRIP LHrcH PLUNGCR

SHAFT RCTHIN1NS COLL
a*eccM BLOC* TRI6SCR SH/trT OCTCN

TIKIM6

MHOLC SHHTT

BREECH MECHANISM.

The breechblock is of the interrupted screw type having four threaded and four plain sectors. It is operated by a handle which swings from left to right, turning and withdrawing the breech with one motion.

An
is

extractor

is

fitted for

throwing out the shell case when the breech

opened

after firing.

167

mechanism; that

mechanism is of the type known as a continuous-pull is, the mechanism is cocked and fired by the pull on the lanyard or by downward pressure on the firing handle located at

The

firing

the left side of the breech.

The carriage

is

composed

of the following principal parts: Wheels,

axle, the cradle (for housing and supporting the recoil of the gun), trail, traversing and elevating mechanisms.

mechanism
is

The gun

carriage

is

of the long-recoil type, in

which the gun

permitted to recoil on the carriage to render the latter stationary under firing stresses. The recoil mechanism consists of an hydraulic cylinder filled with oil, placed parallel to the gun, and attached to the cradle The recoil cylinder controls the backward movement of the gun upon discharge, and the springs function to return the
piece to battery position.

FIRING MECHANISM.

The recoil and counterrecoil mechanism is of the hydro-spring type, and consists of two parallel steel tubes (the spring cylinders) fitted into a frame and surrounded by rails which form the gun slides and the cradle. The recoil cylinder is fitted between these two. The piston and spring rods secured to the gun lug and recoil with the gun, while the spring cylinders and recoil cylinder remain stationary.

The

recoil is of the

constant type, being 70 inches

when

the gun

is

fired at zero elevation, and is somewhat greater at higher angles, due to the action of gravity on the recoiling parts. The recoil cylinder

uses hydroline oil as the buffer medium. Throttling is obtained by three throttling bars running lengthwise of the cylinder, which are
of varying height to

give

a

throttling

effect

with corresponding

slots in the recoil piston. rod to take up the shock

A counterrecoil buffer is fitted in the piston
when
the springs return the gun to battery.

168

169

The trunnions on the cradle are mounted in bearings formed by a yoke which swivels in a pintle bearing provided at the front of the
trail.

obtained. by means of a handwheel and screw mounted on the left side of the trail, which swings the yoke, it carrying the traverse of 70 mils on each side of center is possible. gun with it.
Traverse
is

A

Tho

piece

is

upper end

is

elevated by a double screw type of mechanism. The attached to the cradle and so raises and lowers it.

FRONT VIEW OF CARRIAGE EQUIPPED WITH BAND BRAKES.

The screw
elevation

is operated through gearing by two handwheels, one on each side of the trail. From 5 degrees depression to 15 degrees
is

obtained.

the solid type, made up of flasks of channel section. houses the axle and carries the pintle bearing in which the top A tool box is fitted in the trail, and a carriage, or yoke, swings. seat is provided on each side of the trail for the cannoneers. The lunette transom is fitted about 27 inches from the rear of the trail, and carries a bearing that fits the limber pintle. A trail prop is

The

trail is of

It

170
provided for supporting the trail when limbering. The spade can be released and folded up on the trail when traveling. A traveling lock is provided on the trail for locking the gun when The piston rod and spring rods must be disconnected traveling.
before the

gun can be drawn back

far

enough

to lock.

REAR RIGHT SIDE VIEW OF CARRIAGE.

The wheels are 61 by 6-inch rubber tires, and are equipped with band brakes. Some of the older type of vehicles have steel tires

ELEVATING AND TRAVERSING MECHANISMS.

and are

fitted with tire brakes. An armor plate shield is fitted to the carriage for the protection of the personnel. The sighting is similar to the 3-inch gun, model of 1902.

The instruments
quadrant.

for sighting

sights, a rear sight, a front sight, a

and laying the piece include line panoramic sight, and a range

171

172

and a These are located on the jacket of the gun, and are useful for giving gen eral. direction to the gun. The rear and front sights are used for direct aiming. The rear sight is a peep sight mounted on range scale shanks on left side
line sight consists of a conical point as a front sight

The

V-notch as a rear sight.

REAR VIEW OF CARRIAGE EQUIPPED WITH BAND BRAKES.
of the cradle.

The front sight consists of a pair of cross wires mounted in a ring about three feet ahead of the rear sight. The sight shank has a socket in which the standard United States
panoramic sight

may

be mounted.

the right side of the cradle is mounted the range quadrant, which has in combination with it the angle of sight mechanism. For indirect fire the gunner on the right of the piece lays for range with
this instrument,

On

and the one on the

left lays for direction only.

173

^
i_

in

^

uj

&

&

s

$

V

< < S g < < I r^ruuur< u inuminj^in^ r?
<

o

174
Fixed ammunition
is

plosive shell being used.

used with this gun; shrapnel and high exThe base fuzed stell shell and the shrapnel

FRONT VIEW OF CARRIAGE EQUIPPED WITH TIRE BRAKES.

weigh 60 pounds.

The point fuzed

shells are also issued

sheel weighs 45 pounds. and are identical with the 45-pound steel

Gas
shell.

4.7-INCH

GUN CARRIAGE LIMBER, MODEL OF

1905.

The
riage
is

limber, a two-wheeled vehicle to which the trail of the carfastened, forming, with the gun carriage, a four-wheeled car-

riage for the

gun when

traveling.

carriage limber is designed to be used with the connecting for attachment to a tractor and to support the trail in traveling. pole The limber is made of metal throughout, wood being used only in

The

the spokes and felloes of the wheels. The principal parts are the wheels, axle, frame, top carriage, pole socket, and connecting pole. The top carriage is a steel casting, formed to accommodate "the trail
of the 4.7-inch

gun

carriage, the trail resting

on

it

when en

route.

FRONT VIEW OF LIMBER.

The
rest

front end of the top carriage is provided with three rollers which and run on the top carriage rail; the rail edge being equipped

with clips to prevent accidental dismounting. A spur located on the top carriage which enters the trail, holds the trail and top carriage in
line.

tired.

The wheels are The hubs

51 inches in diameter, 4 inches wide, and are rubber are similar and interchangeable with those on the

wheels of the carriage.
piece of forged steel.

The

axle

is

hollow and

is

made from

a single

bucket holder with straps is located on each side brace for carrying four canvas watering buckets.
18322&
20
12

A

(175)

176

177

The doubletree, singletrees, and pole complete are omitted for motorized batteries and a competing pole is used in their place. The standard short pole with lunette is fitted for motor traction and for horss-drawn equipment the longer pole may be substituted.
Weights and dimensions.

Weight, complete, including spare connecting pole Weight of limber with gun and carriage, traveling position Diameter of wheels (rubber tired)

pounds. do
inches.

.

1,
9,

750
818
51

.

Width

of track

Free height under limber and carriage

do do

60
16.

8

4.7-INCH

GUN

CAISSON,

MODEL OF

1908.

The 4.7-inch gun caisson is constructed upon the same general plan as the 4.7-inch caisson limber. The wheels, axles, pintles and bearings, lock bars, and most of the implement fastenings and chest
parts of the two vehicles are exactly similar and interchangeable. The principle parts of the caisson are the wheels, axle, axle bearings, ammunition chest, pintle, connecting-pole socket, connecting pole, prop, apron, and brake.

The flange-steel front plate and chest door (upper) of the limber are on the caisson replaced by armor plates, for the protection of

RIGHT SIDE VIEW OF CAISSON.

ammunition servers from small arms and shrapnel fire, An apron of armor plate is hinged to the bottom of the caisson chest and extends This to within a short distance of the ground for the same purpose. apron swings forward against the bottom of the ammunition chest to clear obstructions in traveling, and is held in that position by
latches attached to the sides of the chest.

The pole socket of the limber, and is fitted with
connecting body
fit

caisson

is

made

longer than on the caisson The rollers which serve as wheel guards. rear end is finished to of steel tubing, its
is

made

the pole socket, and is provided with a seat for the rectangular key which secures the connecting p6le to the socket. A prop of
(178)

179
tubing with a bronze foot is attached to the connecting pole for a support when the caisson is unlimbered when not in use the prop is swung up under the connecting pole and is held by chains. The beams of the road brake are hinged in brackets riveted to the
steel
;

^

The brakes are built up of flange and forged steel parts and carry cast iron shoes to bear against the wheel tires. Hangers for a spare connecting pole and a bracket for a spare key The ax, hatchet, lantern, and watering are provided on the chest. bucket fastenings are similar, and located like those on the caisson limber. The paulin on the caisson chest serves as a seat cushion and on either side of the chest handrails provide handholds for the
chest front.

cannoneers,
011

when mounting or dismounting. The opening between the upper and lower intermediate
the left side
is

plates

utilized to carry a two-gallon oil. can.

four caissons, three carry oil fourth, hydroline oil, the contents of each being indicated
'

tion chest for the transportation of ammunition for the 4.7 inch gun. The principal parts are the wheels, axle, ammunition chest, pintle,

pole socket, pole, doubletree, singletrees, and neck yoke. Tho wheels and the wheel fastenings are the same as, and are interchangeable with, those on the carriage. The axle is hollow and of a
It is secured to the chest by axle bearsingle piece of forged steel. ings riveted to the sides of the chest and to the flanges of the inter-

mediate plates.

Tho ammunition
into

chest is built up of flange steel and is divided an upper and lower compartment by intermediate plates. Cor-

VIEW SHOWING GUN CAISSON AND LIMBER, LIMBERED.

responding holes in the middle and rear diaphragms are connected by conical brass tubes called connecting pieces, which are cut away on top to save weight. These connecting pieces support the front end of the cartridge case and serve to guide the projectiles. The
chest doors close against the heads of the cases so that the cartridges Suitable clearances are cut in the flange are firmly held in position. of each cartridge pocket to enable the cartridge hook to get back of the rim of the case in withdrawing it from the chest.
is mounted upon a doubletree pin projecting up a boss on the forward end of the pole socket. A limber through prop is hinged to the pole socket. When traveling, the prop is drawn up to the rear and held by a chain. The pintle swivels 300 in the bearing, but is normally held in a

The doubletree

vertical position

by a spring bolted
(180)

to the pintle bearing support.

181

The

right side of this vehicle

is

equipped with fixtures for holding a
left side

pick, hatchet, for a shovel.

and pickax; while on the
of the chest
is

provision

is

made

The paulin on the top
fastened.

held in place

by straps suitably

Other fastenings on top of the chest are for a picket rope, an ax, and a limber blanket. On the front are attachments for a wrench and a pole prop. The cartridge hook for use in withdrawing the cases and projectiles from the chest is fastened on the left side A spanner for tightening the hub bands of the wheels of the caisson. is carried between the intermediate plates. The pole, doubletree and singletrees, and neck yoke arc standard and interchangeable with those on any limber of the battery. Doubletree chains attached to the chest body prevent excessive movement of cither end of the doubletree. The 4.7-inch gun limber, model of 1908, is only used in connection with the 4.7-inch gun caisson, model of 1908, both being of American design and manufacture. These vehicles are used with motorized as well as horse-drawn batteries of 4.7-inch gun materiel.

4.7-INCH

GUN CAISSON, MODEL OF

1916.

The caisson, model of 1916, is a two-wheeled vehicle with an armored ammunition chest for the transportation of ammunition for the 4.7-inch gun. This vehicle is designed to carry 28 rounds of

RIGHT FRONT VIEW SHOWING CHEST DOORS OPEN EXPOSING DIAPHRAGMS.
the fixed type of ammunition. The body is suspended in such a manner that 7 rounds are carried below and 21 above the axle. The chest is built entirely of steel, but the upper door, rear plate, and an apron hung under the body are of armor plate for protection of the ammunition servers in the rear, from shrapnel and small-arms fire. The doors open to the front, and when closed bear on the heads of
Suitable fastenings are provided on this chest for carrythe usual complement of tools and accessories, also brackets for ing
the shells.
(182)

183

184
carrying fuze boxes on the outside of the chest. scats for two cannoneers.

The chest provides

This caisson

is

provided with an ammunition chest of sufficient
It
is

size to carry either shrapnel or high-explosive steel shells.

also equipped with fixtures for holding picks, shovels, and other tools on the outside of the ammunition chest. By removing the

connecting pole, and adding double and singletrees, this vehicle may be transformed into a caisson limber suitable for horse traction.

FRONT VIEW OF GUN CAISSON.

ammunition and connecting pole. chest, pintle, brake, connecting pole socket, The wheels and wheel fastenings are the same as, and are interchangeable with those on the carriage. The axle is fastened to the
principal parts of the vehicle are the wheels, axle,

The

chest

by axle bearings riveted to the chest sides. The body of the chest is of flange steel riveted together forming the top, bottom, and sides of the chest. The chest doors close

in position.

against the heads of the cases so that the cartridges are held firmly Suitable clearances are cut in the flange of each car-

185
tridge pocket to enable the cartridge hook to get back of the rim of the case in withdrawing it from the chest. The chest doors open to

the front, the lower door being hinged to the bottom of the chest, the upper to the top of the chest, and by means of a lock bar, the

doors are locked.

The armor-plate apron is hinged to the bottom of the caisson, so that whoii traveling it may be swung backward against the bottom, where it is held by latches on the chest sides.

The vehicle is equipped with a short connecting pole in front provided with a suitable prop for holding the pole up when the caisson is at rest. At the rear is the standard pintle enabling other vehicles
be connected en train. the tire brake models, brackets are riveted to the end of the To these brackets are pinned the brake beams by the same chest. kind of leverage system as on the carriage. The brake shoes are brought to bear on the tire by pressure on the brake lever, the brake lever and segment being on the left side of the vehicle. The brake band model like the tire brake, has the brake lever on the left side of the chest and is of the contracting band brake type. Pulling up on the brake lever, causes the brake bands to grip the
to

On

drums bolted to the wheels. The top of the chest has provision made for carrying a picket rope and spare connecting pole, an ax, and straps for a paulin that also serves as a seat cushion. The left side carries the pick, mattock and hatchet; the right, a long-handled shovel, cartridge hook and pole socket key. On the back are riveted a bucket holder, lantern bracket
and a foot rest. Between the intermediate plates in front, an oil can is carried on the right side, a fuze box on the left, and also a spanner wrench. In every battery, one caisson is provided with a hand reel containing one mile of wire as for the caisson model of 1917. See page 159.
Weight, dimensions,
etc.

Weight Weight Weight Weight

empty with implements or ammunition implements carried including spare constructing pole of ammunition of caisson fully equipped and loaded Round of ammunition carried Diameter of wheels
of caisson, of of track

pounds. do do do
inches.

.

2,

565

2,

180 067
812
28
61

4,

.

Width

do
..do..

Free height under caisson

60 20.8

4.7-INCH

GUN CAISSON, MODEL OF

1917.

The caisson, model of 1917, is a two-wheeled vehicle equipped with an armored ammunition chest for the transportation of ammuniThe two most important changes from tion for the 4.7-inch gun. models are: The substitution of a band brake for a tire previous
brake, and a spring support for the ammunition chest. The principal parts of the caisson are: The wheels, axles, spring

support, ammunition chest, brakes, pintle, and connecting pole. The wheels are 60-inch, steel tired with standard hubs and fastendistinaxle is a hollow single piece of forged steel. Suitfeature of this caisson is the spring-supported chest. guishing able brackets are provided on the chest and arms on the axle for
ers.

The

A

carrying spiral springs to take up road shocks. The ammunition chest is built up of flanged steel, except the rear The body plate, apron and chest doors, which are of armor plate.
is made of two sheets of flanged steel formed to shape and joined at the sides. Three vertical diaphragms with connecting pieces provided an even distribution of the load of ammunition. The upper door when raised is held at about a 60 angle. The lower door is made with an armor plate apron hinged to its top edge, so that when it is dropped, it forms, with the upper door and rear plate, an armor-plate protection. The road brake is of the contracting band brake type and is operated from the right side of the chest by pulling up on the brake lever; this through a linkage causes the brake bands to grip the drums of the wheels.

of the chest

The connecting pole

is

attached to the caisson by a socket, the

inside being tapered to accommodate the rear pole, also the horse pole.

end

of the connecting-

Two foot rests of commercial flange steel are riveted to the upper chest door; these also serve as handles in opening and raising the door. lantern bracket, and fastenings for holding a pick, shovel, At the lunette, and spanner wrench are riveted to the rear plate.

A

top are riveted fastenings for holding an ax, connecting pole; also strap fastenings for the paulin and the caisson blankets. A cartridge hook and hatchet fastenings are riveted to the left side of the
chest.

Of every four caissons three carry lubricating
oil.

oil

and one hydroline
reel for caisson,

One

caisson in every battery

is

provided with a

(186)

187

188
of 1917, which is riveted to the top of the caisson and contains mile of field wire so arranged that the "talk" goes through all the See page 159. wire. By changing the connecting pole and adding the doubletree and A standard singletrees this caisson is converted into a caisson limber.

model
1

pintle with a semiautomatic latch
Weights

is

provided at the rear.

and dimensions.
pounds.
.

Weight of caisson, empty, without implements or ammunition Weight of implements carried, including spare pole Weight of ammunition Weight of caisson fully equipped and loaded

2,

053
180
067

do do do
inches.
..do..
.

2,

4,

300
28
60

Rounds
Width

of

ammunition carried
wheels

Diameter

of

of track..

60

5-INCH, 60-POUNDER,
The United

GUN MATERIEL

(BRITISH.)

States procured a number of batteries of 5-inch, GO with the necessary accompanying vehicles from Great pounder guns
Britain.

The materiel is of British design and manufacture throughout, and the units ceded to the United States include the gun, Mark I, mounted on a carriage, Mark II; the gun carriage limber, Mark II, the ammunition wagon, Mark II and the ammunition wagon limber,
;

Mark II. The materiel was
thus
is

originally designed for horse transportation and with poles and the necessary attachments for horse provided

REAR LEFT VIEW OF CARRIAGE IN BATTERY.

By substituting the engine-draft connsctor in place of the horse draft poles, the materiel is converted into motorized batteries and may be drawn by tractors. When horse drawn, it is customary to divide the four vehicles into two trains, each having two vehidraft.
cles;

however,

when

the battery

is

adapted for motor draft, the four

vehicles are

drawn

as ons train.

The load of the gun carriage and limber is about as heavy as is practicable for horse transportation, although the British originally designed their 8-inch howitzer materiel, which is of greater weight,
for horse transportation. The carriage is of tlie constant recoil type, the recoil being of the hydro-spring type, located above the gun.

mechanism The recoil

mechanism
filled

consists of two spring cylinders and one hydraulic cylinder with glycerine and water. The piston rod of the recoil cylinder and the rods of the two spring cylinders are connected to the lug on the breech ring of the gun and therefore recoil with the gun.
(189)

190

nl

ag

I

8

191

Upon
The

recoil of

the gun, the liquid

is

forced past the piston head

through a throttling groove or
resistance offered

by

slot cut in the wall of the cylinder. the action of the liquid in the cylinder,

together with the resistance offered by the compression of the springs in the cylinders, controls and absorbs the shock of recoil, permitting the carriage to remain practically stationary upon the ground when
the piece
is fired.

The energy stored up
of the springs

in the spring cylinders due to the compression during recoil is sufficient to cause the gun to return to

is provided at the front of the hydraulic cylinder and acts as a cushion, thereby preventing the violent return of the gun to firing position.

the firing position. A hydraulic counterrecoil buffer

VIEW SHOWING TRAIL CONNECTED TO LIMBER.

A range of 12,280 yards (11,230 meters) is possible, when firing a 60-pound projectile with a muzzle velocity of 2,080 feet per second
at the

maximum
carriage
is

elevation of

21^.

The

equipped with tractor wheels provided with inde-

pendent wheel brakes.

The trail is of the single unit type, being broadened at the spade end and equipped with a fixed spade for anchoring the trail to the
ground.

When

traveling, the carriage

is

connected to the limber by un

adjustable connecter.

The carriage permits elevation from 5 depression to 21 $ elevation. The carriage permits traverse of 4 left and 4 right, when it is elevated at 16^ or less. At higher elevations the traverse is but 3 right and 3 left, due to the interference of the trail with the gun at
these elevations.

18322820

13

192
Weights, dimensions,

and

ballistics.

Weight Weight Weight Weight

of carriage

of

and gun gun and brooch mechanism

pounds.

.

12. 09<i 4.
7,

do. ...

858

of carriage

W

of projectile T eight of powder charge
trail

Pressure of

on ground

do do do .... do ....
inches.
.

238
60

9.

44

Length

of

gun

L6S.

920 05
625

Length, over all. of carriage and limber, traveling position, with gun but without limber pole feet. Length, over all, of carriage and limber, traveling position, with gun and
.

2S.

pole

,

feet.

.

37. 5
13.

Length between axles, of carriage and limber, traveling position Height of axis of gun from ground

Track, center line to center line of wheels Diameter of turning circle

do ...
.
.

63. 5

.

.

54

5-INCH, 60-POUNDER GUN, MARK I, MARK II (BRITISH).
wound type and

AND CARRIAGE,

The gun

is

of the wire

consists of

two tubes,

jacket, breech bush, breech ring,

and several layers

of steel wire.

The inner tube extends the length of the barrel, the outer tube being shrunk upon it, extending over the rear of the inner tube to form a threaded bearing for the breech bush which receives the breech block. The jacket is fitted over the tubes and extends to the rear, having
a threaded section on which the breech ring is received. Several layers of steel wire are interposed between the jacket and tubes, the jacket being shrunk over the wire. The breech ring is provided at the top with a lug, to which the recoil piston rod and the rods of

the spring cylinders are secured, being the direct connection between the gun and recoil mechanism, and is provided with lugs at the right

j

On either side of the acket longitudinal pro] ections are provided, which engage and slide in corresponding slots in the cradle.
side

which accommodate the breech

carrier.

.

The breech block is of the interrupted screw type, having threaded and slotted sectors. The breech bushing is threaded and recessed to correspond with the sectors on the breech block. The breech is so arranged that by one pull of the breech lever from mechanism left to right the breech screw is unlocked and the screw and carrier

swung
turns

into loading position. After loading, one thrust of the same lever inserts the breech screw into position in the breech bush and
it

into the locked position.
is

The breech screw

supported by the

carrier,

which pivots and

is

hinged to the lugs provided on the right side of the breech ring. The firing mechanism is of the "T" type and is fitted with a safety
device which prohibits the firing of the gun until the breech is closed. Discharge is by means of a lanyard operated from the right side of
the carriage.

The carriage consists of the following major parts: Cradle, including mechanism; top carriage; elevating and traversing mechanisms; trail; brake gear; wheels and axle. The carriage is constructed on the long recoil principle, having
recoil

The length practically a constant length of recoil at all elevations. of recoil is approximately 57 inches. The recoil mechanism is placed
parallel with, and located above the gun, the gun sliding recoil and counterrecoil in slides provided in the cradle.
(193)

during

194
The recoil mechanism being of the hydro-spring type, utilizes two spring cylinders and one hydraulic cylinder, independent of each The cradle is other, and held in relative position by the cradle. in form and incloses the breech end of the gun, and is cylindrical
provided with threaded holes at the front and rear for the reception of the spring and hydraulic cylinders, which are screwed into these holes. The three cylinders extend to the rear and engage suitable holes in the breech ring to which they are fastened by connecting pieces, the two spring cylinder rods being retained by nuts, and the hydraulic cylinder rod by an externally threaded collar which passes through the breech ring and engages the thread on the piston rod, the three rods recoiling to the rear with the gun.

The trunnions
carriage, permit traverse.

which

in turn

of the cradle are received in bearings in the top is pivoted on the front end of the trail to

Traverse and elevation is accomplished through the medium of handwheels located on the left side of the carriage. The elevating

REAR RIGHT VIEW OF CARRIAGE.

handwheel actuates a pinion meshing with a rack bolted to the The traversing handwheel operates a screw, one end of cradle. which is hinged on the top carriage, the other end engaging a nut which pivots on the trail. Traversing stops are provided on either side of the top carriage to limit the traverse to 4 right and 4 left, when the gun is elevated
at-

16^

or

less.

a pointer fixed to the trail, which reads to a graduated scale on the rear transom of the carriage. The trail is of the solid type, being cut out at the front to give clearance to the breech of the gun during recoil, and at high eleva-

The amount

of traverse

is

indicated

by

tions.

The

front end of the trail

is

through which the axle Dasses.

The

equipped with bronze brackets trail has a bearing at the

195
forward section on which the top carriage rests and pivots, and through which the pivot pin passes, retaining the top carriage in proper position. Clips are provided on the trail which engage protrusions on the top carriage, preventing vertical movement of the top carriage when the gun is fired. Traversing stops are provided to prohibit traversing of more than 3 left and 8 right, when the gun is elevated above 16^. The rear end of the trail is equipped with a connector for limbering The connection is held in the carriage to the carriage limber. and is provided with holes for adjustment. position by pins, A spade of the fixed type is riveted to the rear end, and holds the
trail in

A
is

a practically stationary position when the gun is in action. traveling lock is provided on the trail which engages the breech

of the

gun

at

degree elevation,

to the inside of the trail

when traveling. The lock is hinged members and swings down when the gun

in firing position. The wheels are of the tractor type, being provided with diagonal The wheels are 60 inches in diameter cleats riveted to the rims.

and have

tires 12
is

inches in width.

provided on each wheel against which an internal brake shoe is fitted, which is operated by a handwheel at the front of the carriage. Sighting is accomplished by means of a tangent sight and foresight
brake ring
sight (panoramic sight)

A

on the right side of the carriage, and by an oscillating sight and dial on the left side of the carriage. The tangent and foresight together form an open sight for the
direct laying of the gun.

The oscillating sight on which the dial sight is mounted is used for indirect laying; the oscillating sight being used for laying in elevation and the dial sight for direction.
Ammunition of the separate loading type is used, being both explosive shell and shrapnel. The weight of each is 60 pounds.
consists of 9 pounds 7 ounces of cordite. Normally these charges are not separate for zone fire, although special charges are sometimes made up for this purpose.

The propelling charge

5-INCH, 60-POUNDER,

GUN CARRIAGE LIMBER,
II

MARK
The limber
consists

(BRITISH).

mainly of a

steel frame,

two

steel chests,

wheels, axle, and draft connections. The vehicle is designed for 2-horse,

4-horse,

or tractor draft.

horse drawn, the front end of the frame is equipped with a wooden horse pole, which is retained in place by a pin passing vertically through the rail and pole, and is also equipped with two or four singletrees, as the draft may require. Chains, with the neces-

When

sary draft connections, are also provided, and extend from two points on the frame to the forward section of the pole, thereby adapting the vehicle for additional horse draft. The necessary neck yoke bars are provided on the draft pole.

FRONT VIEW OF CARRIAGE LIMBER.

For 4-horse draft, the two outside singletrees are suspended from outriggers which are hinged to the main frame, and are steadied by stays extending back to the axle arms. For 2-horse draft, the two outside singletrees are removed, the stays disconnected, and the outriggers folded back and over the main frame, being held in the latter position by straps.

The

singletrees,

when removed,

are strapped across the center of

the frame forward of the steel chests.

For tractor

draft, all the singletrees are

the frame, the horse pole being removed and replaced draft connector, which is pinned to the frame.
(196)

removed and strapped to by the motor

197

The frame consists principally of four side rails, two inner and two outer, connected at the rear to the axle by flanges and pins. The front end is joined together by connecting plates, the frame
being strengthened by diagonal stays. In the rear of the frame at the center, a pintle is provided, which accommodates the adjustable connector on the trail of the carriage The pintle is provided with a thumb latch in traveling position. which prevents accidental unlimbering of the trail connector. The steel chests are riveted to the main frame at the rear, on either side. The inner rear corners of these chests are formed diagonally

REAR VIEW OF CARRIAGE LIMBER.
to -allow clearance to the swing of the connector

on the carriage,

when traveling. The chests are
at the front side

of flanged steel, having lift lids which are hinged and are equipped with hasps, locks, and chains at the rear. The interior of each chest is fitted for carrying stores, and each is provided at the top with a tray which carries small stores. The left chest is constructed to carry the sights and attachments, together with a number of small tools, and one powder charge in a tin box. The right chest carries the clinometer, oil can, and other various tools and accessories, together with one powder charge in

a tin box.

Extending from the base of each chest toward the rear a steel bracket is provided on which one round of ammunition is carried.

198
shell is held in a vertical position on this support hy a hronze bracket and a strap. Suspended below the frame at the rear, a wire net tray is provided for carrying drag ropes and lashings. Forward of the steel chests, on the top of the frame, a board is fastened, extending across the frame, and is equipped with friction
clips for the

The

accommodation

of

two

rifles.

The wheels provided are 60 inches in diameter, having steel tires The outer end of the axle arms are equipped with 6 inches in width. washers to assist hauling. No brakes are provided on this drag
vehicle.
Weights, dimensions,
etc.

Weight without two projectiles Weight on limber pintle, traveling position Weight on pole, carriage limber (at center tug hole) Without two projectiles With two projectiles
Diameter of wheels Track of wheels, center line to center line
Length:

The wagon is constructed to carry 24 rounds of ammunition, 24 powder charges in tin containers, and 2 fuze boxes. The exterior is fitted with fastenings to carry ropes, handspikes, also other tools
and
accessories.

Q.

u

FRONT VIEW OF AMMUNITION WAGON.
chest is constructed of flange steel, having flange either side at the center, which extend below the chest, providing bearings which receive the axle. The interior of the chest is divided into a front section and a rear

The ammunition
on

steel brackets

section, by a vertical steel plate, passing through the chest, parallel to the axle. Each section is divided by steel plates passing crosswise

through the chest into three horizontal rows of compartments. The lower compartments contain 4 high explosive shell and 4 shrapnel.

The middle row contains

2

high-explosive
(199)

shell,

2

shrapnel, 2

200

powder charges in tin containers, 1 fuze box containing 14 fuzes, and 1 empty compartment. The upper row of compartments contain 10 powder charges in tin containers. The powder charge containers, and the shell are retained in the proper position by quick release straps, and the shell are withdrawn from their respective compartments by means of the packing blocks which inclose the nose of the shell, and by the withdrawing straps provided. The withdrawing straps extend the length of the shell and are fastened to the nose blocks, and are also riveted to the compartment
plates,

preventing their complete removal.

When

the

:

-*^ZlL^-

-

j^-^**-*^lll^XS^^-.-*

=*- -

-

**-"

*~

REAR VIEW OF AMMUNITION WAGON.
shell
is withdrawn about half its length, the withdrawing strap is slipped over the base of shell allowing the complete removal of the shell, while the packing blocks and straps are held in their respective compartments. The powder charge containers can be lifted out

without the aid of straps.

The front compartment is equipped with a steel door which is hinged at the bottom and swings downward when opened. The rear compartment is equipped with an armor-plate door hinged at its lower edge, and when opened hangs vertically downward. The front door when opened downward is supported by the footboard

201
in a horizontal position.

Each door when

closed

is

held in position

sides of the chests, which swing over and engage steel handgrips riveted on either edge of the door at the top. Extending above the chest at the front on either side, handrails

by latches provided on the

are provided.

The

rails are

with leather guards.

The

rails fit into

constructed of steel and are provided small brackets riveted to the

chest sides, and may be dismounted from tjie chest by removing the retaining pins. Three grip straps are also fastened to the upper front edge of the chest to assist the personnel when mounting the
vehicle.

Straps are provided with the usual fastenings, at the top of the chest accommodate the soldiers' personal equipment, and also picket ropes, at the rear. At the front of the chest the fastenings accommodate blankets, lamps, and tool cases. On either side of the chest
to

fastenings are provided, the left side accommodating a case, and the right side a spanner wrench.

saw in

a leather

two flanged sides connected by cross stays which consists of two flange steel members extending back, the length of the vehicle. The outside rails are provided with The chest is flanges and holes through which the axle passes. mounted on the frame, the axle brackets on the chest corresponding with the flanges on the side rails, making a solid bearing for the axle, which is held in place by keys.
consists of

The frame

to the draft pole,

Forward of the chest, across the side rails, a wooden footboard and platform is provided. Suspended below the footboard on either side, is a fuze locker, which provides carrying compartments for 30 fuzes, 15 in each locker. Each locker is provided with a door, which swings downward when opened, arid each is equipped with a hasp and a pivot thumb lock. Suspended from the platform to the rear of the right fuze locker,
pounds of grease, is strapped. The frame is provided at the rear with a steel prop which swings up to the right side of the frame and is retained in this position by a spring clip when in traveling position.
Wire-net receptacles are suspended under the rear section of the frame on either side of the prop bracket. The receptacles provide space for canvas watering buckets and ropes. The draft pole, which is an extension of the center rail of the frame, is joined at its extreme forward end by a lunette, which engages the pintle on the ammunition wagon limber when in traveling position.

a tin box, containing 3

when

pole prop is also provided for supporting the draft pole wagon is unlimbered. The prop swings up to a horizontal Attachments on position when the wagon is in traveling position. the underside support a jointed draft pole and a handspike.

A

the

202
Tire brakes are provided for each wheel, the brake system being operated as one unit. The shoes which bear against the wheel are supported by brackets fastened to the side rails at the front.

The shoes are operated by a crank located on the left rear side of the vehicle under the frame. The crank is connected to the shoes by rods supported on the frame.
of the wooden type, 56 inches in diameter, having steel 3 inches in width, are provided on this vehicle. They are retained on the axle by means of an adjusting collar and linch pin.

Wheels

tires

AMMUNITION WAGON AND AMMUNITION WAGON LIMBER, LIMBERED.

The bearing

is protected from dirt and other foreign matter by a dust cap which fastens over the end of the hub box. Drag washers are provided on each wheel to which ropes may be

fastened to assist in the maneuvering of the vehicle.
Weights, dimensions,
etc.

wagon, empty wagon, loaded and equipped Pressure of wagon pole on limber pintle, loaded Pressure of wagon pole on limber pintle with two
of

Weight Weight

of

men

pounds do do on wagon, loaded .. do ....
. .
'

1, 3,

732
556

98
196
5.

Height to top
Width, Length

of

handrail

.

.

.feet.

.

.

229

Height, handrails removed

do

.

.

.

4.416
6.291

maximum
of

do.

.

.

wagon
,

do

.

.

.

Greatest projection beyond track of wheels Wheel track

inches.

9.708 6.25
63

do.
. .

.

.

Diameter

of

wheels ...

do

.

.

56

5-INCH, 60-POUNDER,

AMMUNITION WAGON LIMBER,
II

MARK
I'u/c

(BRITISH).

The limber comprises the frame with pintle; ammunition chest: locker: draft fittings: wheels and axle. The limber is designed to draw the ammunition wagon by means The vehicle is e -pupped for of the pintle provided at the rear. 2-horse draft. It carries 16 rounds of ammunition together with
Provision is also made to carry the necessary powder charges. 43 fuzes. 28 of which are carried in the ammunition chest, and the remainder in the fuze locker fastened to the top of the chest. Implement fastenings are fastened on the exterior of the chest and foot-

FRONT VIEW OF AMMUNITION WAGON LIMBER.
board, and accommodate
rifles,

blankets, "and the customary tools
is

and

accessories.
is

The chest
three doors.

constructed of steel and

provided at the rear with

The interior of the chest is subdivided by two steel plates into three main divisions, access to each being at the rear. Each division is separated by cross plates into four rows of compartments, the lower two rows of each division being subdivided into smaller compartments to accommodate a total of eight high explosive

and eight shrapnel

shells.

The two upper rows of the two outside divisions are constructed to accommodate a total of 16 powder charges, each protected by
tin containers.
(203)

204

The two upper rows of compartments in the middle division accommodate a tray for small stores, such as cotton waste, pins, pliers, and other small tools; and 2 fuze boxes, each containing 14 fuzes. The fuze boxes occupy the upper row of compartments. The powder-charge containers and the shell are retained in place in the chest by quick-release straps, and the shells are withdrawn from the compartments by withdrawing straps and blocks, identical with those on the ammunition wagon.

REAR VIEW OF AMMUNITION WAGON LIMBER.

A door is provided at the rear of the chest for each main compartment. The two outer doors are of armor plate and have hinges at the bottom edges, and when opened hang down vertically from the chest. A small armor-plate apron is hinged to each door at its upper edge. The aprons hang vertically from the door when each door is opened, and form an extension toward the ground, thereby
giving
additional

protection for the personnel serving the gun.

in closed position, the aprons fold down over the outside of the door and are retained in position by latches fastened to the upper part of the chest, which engage steel hand grips riveted

When

the door

is

to the aprons.

205
is equipped with a steel door which is and when opened, rests over the top of the hinged at the upper edge, The spring latches with thumb lift grips are riveted to the chest: door which engage suitable latches on the lower edge of the chest when the door is in the closed position. Two small clips which extend

The middle compartment

over the edge of the side, at the lower sides, act as retainers for the when they are closed. In operation the middle door is first opened, thereby removing the clips which bear against the outside doors, allowing the outer doors In closing the chest the two outer doors are to be swung open.
outer doors
closed
first.

by leather, are provided on either side of the and extend above the chest. They engage suitable brackets chest, riveted to the chest, to which they are fastened by pins. By the removal of the retaining pins, the handrails may be dismounted from
Handrails, protected

the chest.
is fitted with implement fastenings and the front plate having spring catches for three rifles. Three straps, grip straps are fastened to the upper edge of the chest at the front,

The

exterior of the chest

to assist the personnel in riding on this vehicle. Three leather pockets, one on the rear middle door
either side of the chest, are provided for carrying fuze

and one on and limber

keys.

A wooden locker for carrying fuzes is fastened by steel straps to the
top of the chest on the left side. The locker is equipped with a lift hinged at the front and provided with a hasp and thumb lock at the front. The interior is constructed to carry 15 fuzes. Two blankets, which serve as a seat cushion, are strapped to the top of the chest at the front, and the soldiers' personal equipment is strapped at the rear.
lid,

Each side of the chest has riveted thereto a steel bracket, which extends below the chest body, and is provided with an opening through which the axle passes. The frame which supports the ammunition chest consists mainly of two side rails, two middle rails, and the connecting cross rails. The middle rails are connected at the front of the frame to form a seat for the wooden horse pole. The outer rails converge slightly at the front, and with the middle rails form a support for the wooden platform and footboard. Two of the cross rails extend across the frame, directly beneath the edges of the chest, giving a solid support to which the chest is fastened. The other cross rail extends across the extreme front of the frame and is fitted with hooks for the support of two singletrees. A wooden horse pole, equipped with a neck yoke
bar,
is

Forward
to the

provided. of the chest a

upper side of the frame.

wooden footboard and platform is fastened The boards have staples for the

206

accommodation of leather straps, which secure rope lashings, shovels, and other similar equipment to the footboards. On the under forward right side of the frame a -case is provided to
carry a holo. On the left side of the frame, in a corresponding position, a case is provided, to carry a water brush. Suspended from under the wooden .platform, on the left side, is a box containing 3 pounds of grease. Under the right side of the platform, fastenings are provided to carry two cans containing
lubricating
oil.

which engages the lunette on the draft pole of the ammunition wagon, is provided in the frame at the rear. In each side rail at the rear a hole is provided which forms a bearing The steel axle bracket on the sides of the chest correfor the axle. with these holes, and form a solid bearing for the axle, which spond
held in place by keys. Wheels of the wooden type, 56 inches in diameter, having steel tires An adjusting collar and linchpin 3 inches in width, are provided. screws the wheel to the axle. Protection against the ingress of dirt and foreign matter is provided by a dust cap which fastens over the
is

A pintle,

end

of the

hub box.

Drag washers to assist in the maneuvering of the vehicle are provided on each wheel. The wheels and axle of the limber are interchangeable with those on the ammunition wagon. No brake is provided on the ammunition

wagon
Weight Weight Weight Weight Weight Weight Weight

limber.
Weights, dimensions,
of limber, of limber, of of
etc.

empty
loaded and equipped

pounds. do
-

.

1,

416 632 148
188

2, 3,
6,
1,

do do of do of limber only, with wagon limbered up, loaded of limber pole at position of center tug hole with wagon limbered up, pounds loaded, without men Weight of limber pole at position of center tug hole with wagon limbered up, pounds loaded, with 2 men on limber only y Weight of limber pole at position of center tug hole with wagon limbered up, pounds loaded, with 2 men on limber and 2 men on wagon feet Length of limber with pole do .... Length of limber without pole do Length of limber and wagon, overall do Length between axles of limber and wagon do Height of limber to top of handrails do .... Height of limber, handrails removed do Width of limber, maximum
..

Recent experience indicated the necessity of artillery of larger than the 75 millimeter, having a longer range and better characteristics, yet mobile enough to permit its use by combat divi-

This necessity led to the adoption of the 155 millimeter The importance of this caliber corresponding to 6.10-inch artillery. 155-millimeter howitzer is evident when it is realized that it is the
largest weapon at the present time that can be used by combat divisions, and is especially valuable for use against captive balloons, counter battery firing, and interdiction.

The type of 155-millimeter howitzer carriage adopted is known by the French as the 155 millimeter Court Schneider, model of 1917, and by the United States as the 155-millimeter howitzer carriage, model of 1918 (Schneider). The howitzers manufactured in the United States

RIGHT SIDE VIEW OF CARRIAGE

IN

TRAVELING POSITION.

are also distinguished from those made in France by the designation "Model of 1918." The American materiel differs from the French
in

having a straight shield instead of a curved one, rubber instead of steel tires, a slightly different firing mechanism, and several other

minor changes.

The howitzer

is

mounted on a

carriage having a

At the front end single trail composed of two pressed steel flasks. these are connected by the axle housing and at the rear by a fixed
spade.

The carriage embodies many ingenious features designed to reduce the weight and insure stability. The recoil mechanism is of the hydropneumatic type, the sleigh

In recoiling the liquid is forced from one recoiling with the howitzer. side of the piston to the other though a variable orifice which gradually closes until the howitzer
is

brought to a stop.

The return

of

18322820

14

(207)

208

209
the howitzer into battery
recoil.
is

effected

by the expansion
of recoil
.

of the air

com-

practically constant, pressed during and in order to allow the howitzer to be fired at high elevations

The length

is

without digging in the

trail,

the trail

is

made

of a

curved shape.

FRONT VIEW OF CARRIAGE

IN BATTERY.

By sliding transversely along its axle the howitzer is capable of Its maximum elevation is traversing through a total angle of 6. approximately 42. It fires a 95-pound projectile with a muzzle velocity of about 1,480 feet per second to a maximum range of about
12,300 yards. Separate loading ammunition is employed. By the use of the reduced powder charges, shorter ranges are reached with

SIDE VIEW OF CARRIAGE EN ROUTE.

steep angles of
is

wear on the gun. Its life, before relining necessary, approximately 7,000 rounds. The entire equipment is motorized and the equipment for each
fall

and with
is

less

howitzer includes a carriage limber, used when traveling to support the trail, three caissons or ammunition vehicles, and a number of ammunition, repair, and supply trucks.

hydropneumatic long-recoil type, which may be used for direct fire, but was specially designed for indirect fire. On account of its high trajectory it is able to direct shells on targets inaccessible to field
guns of limited elevation. This howitzer has given satisfactory results in actual service and has proven to be superior to other howitzers of similar caliber. It has a muzzle velocity of 1,480 feet per second and attains a maxi-

mum range of 12,300 yards, the projectile weighing approximately 95 pounds. A maximum rate of fire of four rounds per minute may be attained, but heating as well as difficulty of preparing and serving of ammunition by the gun crew renders such rate impossible for any length of The normal rate of fire is two per minute. time, however. The howitzer is mounted on a sleigh and rigidly secured by a breech key and a holding-down band. The sleigh contains the
mechanism which permits long recoil and insures stability at low elevations. When the gun is fired, the sleigh recoils on bronze slides on the cradle, which is a U-shaped steel' plate and rests on the
recoil

trunnion bearing of the trail. This howitzer may be elevated from zero to 42 by means of the elevating mechanism. The traverse is 52.5 mils to the right and left, the carriage sliding on the axle and pivoting on the spade, which prevents the carriage from recoiling when the gun is fired. The customary shield affords protection for the gunners from shrapnel and
flying fragments.

In traveling position the howitzer

is

retracted and locked to the

cradle, the cradle locked to the trail, the spade revolved and secured to the bottom of the trail. The lower end of the trail rests on the car-

riage limber, which load of the howitzer

is

used to carry

its

proportionate share of the

in traveling position. The limber is equipped with a connecting pole for motor traction. The carriage and limber wheels are rubber tired and considered able to negotiate

The howitzer, carriage, and limber are of the French design and were manufactured in the United States. The caisson is of American design and manufacture. This materiel is used with motorized batteries, and a full complement of tractors
and trucks
battery.
is

provided for the transportation and service of the

The cart, model of 1918, and reel, model of 1909M1, described with the 75-millimeter materiel, are also used with this materiel.
Weights, dimensions, ballistics,
etc.

Weight of howitzer and carriage, iully equipped Weight of carriage complete, but without equipment Diameter of carriage wheels

do
inches.
.

4,

729 53
60

Width of carriage track Normal length of recoil
Elevation

do do ....
(52^ mils; right

51. 30

to 42

20

Maximum

traverse (3

and

3

(52^ mils)

left;.

Weight of limber, completely equipped Diameter of limber wheels

pounds.
inches.

.

1,

440
82 61

.

42.

Width

of

limber track
of 155-millirneter howitzer,

do
limber and carriage limbered
degrees
.

Turning angle

.

.

52

214

215

155-MILLIMETER HOWITZER AND CARRIAGE, MODEL

OF
The howitzer

1918

(SCHNEIDER).

is of the built-up type and consists of a tube and a jacket shrunk over its rear half. The breech end is equipped having with a counterweight which is fitted with leveling plates to be used

with a gunner's quadrant when setting elevations. Below the breech is the bridle which couples the gun to the sleigh and on the forward end of the howitzer a holding down band also functions to secure the tube to the sleigh. The breech mechanism is of the plastic obturator type with an interrupted screw type breechblock. The breechblock is hinged at the right and by means of one motion of the breech lever can be rotated and swung clear of the breech. The forward mushroom-shaped head of the breechblock is equipped with a flexible asbestos ring known as the obturator pad. The gas check pad or plastic obturator is composed of a mixture of one part asbestos and three parts nonfluid oil, contained in a canvas coverThe pad is protected by the front, rear and small split rings. ing. A steel filling-in disk is placed between the gas check pad and the breechblock. On firing, the asbestos ring is compressed and acts as a gas check to prevent the leakage of powder gases back through the The asbestos pad, by its shape, causes the split rings to breech. spread when pressure is applied on the mushroom head. It has
recess

resume its original form after firing. The firing mechanism is of the French percussion primer type. The primer is fired by means of the firing pin driven forward by a hammer operated by the lanyard. The firing pin is supported in the firing mechanism block, which is unscrewed each time a new primer is inserted. A safety device is used in connection with the firing mechanism block, which makes it impossible to unlock the breech
sufficient resiliency to

while the block
is

is

in position, or to insert the block while the breech
is

unlocked. The firing mechanism block those used in the following weapons:

type of recoil is known as constant, i. e., the of recoil is not shortened at high elevations. The sleigh length contains the recoil mechanisms and serves as a support for the
this howitzer the
(216)

With

217

218

219
howitzer, being secured to
it by the breech lug ana the nolding howitzer and sleigh move on the cradle recoiling, fastened to the trunnions of the carriage, the piston rods remaining

down band.

On

stationary.

A mixture of
and
anism.

glycerine and water (boiled) is used in the recoil brake to that mixture caustic soda is added for the counterrecoil mech-

The gas used

in the counterrecoil

mechanism may be

either

air or nitrogen.

Nitrogen is always used when available, as it has no corrosive action on the mechanism. The energy of recoil is absorbed by the friction of the liquid while passing through the openings in and around the recoil piston and by the compression of the nitrogen in the cylinders. The howitzer is returned to battery by the energy stored in the compressed nitrogen which forces the liquid out and reacts against the
counterrecoil piston.
is

When

in battery, the initial nitrogen pressure

approximately 485 pounds per square inch, which is sufficient to hold the howitzer in battery at all angles of elevation. Gages are provided to indicate both the quantity of liquid and nitrogen pressure. Suitable pumps are provided with the materiel for pumping in
liquid
air. Cylinders of compressed nitrogen are carried to the supply of nitrogen. replenish The cradle is secured in the trunnions of the carriage and supports

and

the sleigh during recoil. To the underside of the cradle are fastened two elevating arcs; thus the howitzer is elevated by means of the handwheel located on the left side of the carriage, and elevations from to 42 20' may be obtained.
of the carriage is obtained by the traversing mechanism the carriage to slide on the axle, the trail pivoting on the causing spade. The movement is 3 each side of the center, or a total of

The traverse

The movement is obtained by means of a traversing nut fastened to the axle, causing a traversing screw to travel rigidly carrying the carriage along the axle. The carriage travels along the axle on rollers mounted on Belleville springs. When the gun is fired, the springs are compressed and the carriage rests on the axle. A lock is provided for relieving the strain on the traversing and
105 mils.
elevating mechanisms when traveling. Two traversing handwheels are provided, one on each side of the carriage.

The wheels are of wood, 1,350 millimeters (53 inches) and are fitted with solid rubber tires. The carriage with a pair of brakes acting directly on the rubber tires.

in diameter
is

equipped

An armorarms

plate shield for the protection of the personnel against small

and shrapnel
Sighting
sight,
is

fire is also

provided.

accomplished by means of a quadrant sight, panoramic
sight.

and peep

220

221

222
sight, model of 1918 (Schneider), is mounted on trunnion of the carriage. It is used for laying the piece in elevation. The angle of site mechanism is combined with this sight. Mounted on the top of the quadrant sight is the United States panoramic sight for laying the piece in traverse. An extension bar is provided for use with the panoramic sight to enable the sight to be raised enough to see over the shield or other obstructions in direct

The quadrant
left

the

aiming.

The peep sight, used only in mounted on the quadrant sight

direct

fire,

or in emergency,

may

be

in place of the

panoramic

sight.

complete sets of night-sighting equipment are provided for use when firing at night. When not in use these equipments are packed in cases provided for that purpose and carried on the carriage limber

Two

The night lighting equipment consists principally
and
fixtures.

of a chest, an aiming lamp, an azimuth lamp, a portable lamp, and the necessary cables

155-MILLIMETER HOWITZER CARRIAGE LIMBER,

MODEL OF
The 1 55-millimeter ho witzer
employed

1918

(SCHNEIDER).
is

carriage limber

a two-wheeled vehicle

to support the trail of the carriage when traveling. This limber consists of a built-up steel frame mounted on wheels and axle.

It has

The

no chests and provides no seats for the personnel. pintle is riveted to the extreme rear end of the frame and

serves as a bearing for the lunette of the carriage when the howitzer is limbered. Additional support for the trail is provided by a trail
rest riveted in front of the pintle trail bears.

and on which the

fifth

wheel of the

Hooks

are provided for carrying a picket rope,

for carrying grease

and small boxes and the night lighting equipment are secured on

the frame.

on the front of the frame for holding the limber The standard short pole with the lunette for motor traction batteries is provided, or the long pole may be substituted for horse-drawn equipment.

caisson is a two-wheeled spring supvehicle for the transportation of ammunition. ported Normally it is a motorized vehicle, two caissons forming a train drawn by one

However, by removing the connecting pole and substitutthe standard pole the front vehicle of the train can be converted ing into a horse-drawn caisson limber. Any caisson in the battery
tractor.

REAR VIEW OF CAISSON.
except the caisson equipped with the hand reel can be so converted The caisson carries 14 complete rounds of ammunition and 2 extra powder charges for the 155-millimeter
howitzer.

into a caisson limber.

lower and upper chest body and rear plate, plate. The chest is divided into an upper and lower compartment, the opening between them forming a space for the axle, pole socket, pintle bracket, and houses the fuze box and oil can.
chest
is

The

made up
of

of the

which

is

armor

(225)

226

227

The upper compartment is arranged for the transportation of Powder is served to the 8 projectiles and 16 powder charges. each containing 2 powder charges. The caissons in fiber containers, container is fitted with an air-tight joint metal cover and base. The
lower compartment is arranged for the transportation of 6 projectiles. The upper chest door when closed forms a cover for the chest and is
held open by door props. When open, this armor plate door serves as a shield for the cannoneers.

The lower compartment is also provided with an armor plate door hinged to the bottom of the chest body, and has an armor plate
apron hinged to its edge. When open, the lower chest door and apron hang down, forming a shield for the cannoneers. When closed, this door forms a cover for the lower compartment; the apron doubles back against the lower chest door and is latched in place. Both compartments are provided with loose diaphragms, by the use of which the caisson can be made available for transporting any
of the following types of shells
:

Only one type of shell can be carried in the same compartment at one time. When carrying either common steel, gas, or shrapnel, the
loose diaphragms are placed in position after the projectiles are inserted in the projectile tubes. When the doors are closed (carrying either common steel or gas shells) the door stiffeners bear against

the bases of the projectiles, holding them in place. With shrapnel the edges of the flanged holes in the loose diaphragm bear against

mon

the rotating bands of the projectiles. When used to transport comsteel shells Mark IV the loose diaphragms are placed inside the When the doors body of the caisson next to the front diaphragms. are closed the door stiff eners bear against the bases of the projectiles,

them firmly against the loose diaphragms. and grip straps are provided on the chest for the convenience of its personnel. The outside of the chest is provided with implement fastenings for the usual complement of. accompanying tools and accessories. Blanket straps are provided on
holding

Foot

rests, handrails,

top of the chest for carrying the blanket rolls of the battery personnel; provision also is made on top of the chest for carrying the connecting pole and on the rear for carrying the lunette and caisson prop when used as a horse-drawn vehicle.

The caisson prop when down serves to support the front end of the caisson; in traveling it is swung up and held by the prop chain. The axle passes through the caisson between the upper and lower intermediate plates. Axle brackets are clamped on either end of the axle just outside of the chest, and rotation or lateral motion of the

228
chest is prevented by clamp screws and Belleville springs. The chest has a spring suspension similar to that of the 4.7-inch gun caisson, model of 1917, for the relief of road shocks. The caisson is provided with a brake mechanism of the band type. The brake drums are mounted on the hub boxes of the wheels and the band brakes lined with Raybestos. A brake lever secured to a bracket riveted to the caisson body, functions as a means by which the brakes may be applied. The caisson is usually equipped with the short pole for motor traction, but the pole socket is designed so that the long pole may be used when desired to use the vehicle as a horse-drawn limber. A

FRONT VIEW OF CAISSON.
standard pintle
vehicles.
is

fitted at the rear for the

connection of the other

One

caisson in each battery

is

equipped with a reel for caisson,

model of 1917. This is a hand-operated reel for the transportation and handling of telephone wire. Se.e page 159.
Weights and dimensions.

The type of 155-millimeter field gun adopted is known by the French as the'"G. P. F." (Grande Puissance Filloux), and by the United States as the model of 1918. This caliber, which corresponds to 6-inch artillery, is the heaviest mobile artillery, exclusive of the heavy howitzers and the railroad artillery. This monster weapon is of rugged design, combining mobility and power, and has a large horizontal training angle to render it suitable
for the concentration of artillery fire for the destruction of strongly fortified points, such as armored batteries, etc.; thus no other avail-

able weapon of equivalent caliber can be considered to rival this type. This piece, like the 155-millimeter howitzer, is especially valuable in

TRAVELING POSITION (RIGHT
firing

SIDE).

against captive balloons, counter battery firing,

and

inter-

diction.

The Filloux gun is mounted on a carriage having a split trail of box girder section; which is spread out when in action, the ends of the trail being firmly anchored by spades in the ground. The splittrail effect permits clearance for recoil at high elevations and allows a firing over a horizontal field of 60 and an elevation varying from to 35.
Its muzzle velocity is about 2,411 feet per second, a rate of propulsion that throws its projectile weighing 95 pounds, approximately 17,700 yards, or a little more than 10 miles. The gun recoils in slides formed in the cradle which rests in the

trunnions of the top carriage. The length of recoil is automatically controlled and varies with the elevation, while the counter recoil is pneumatic. The entire recoil mechanism is commonly called the
recuperator and
is

supported on the carriage at
(229)

its

trunnions.

When

230

231
traveling,
a
tlio trail is

closed up and the ends thereof are supported

carriage limber provided with a steering gear brake, by a tractor. In traveling position both carriage

by and is drawn and carriage
all

limber are supported on semielliptical springs to absorb shocks and vibrations.

road

REAR VIEW OF CARRIAGE

IN

BATTERY POSITION.

The The

life

of the

gun before

3,000 rounds and
entire

maximum
is

relining becomes necessary is about rate of fire is two rounds per minute.

equipment

motorized.

A

carriage

limber,

which

supports the trails in traveling, accompanied each gun. Caissons are not used with these guns, the ammunition being carried in motor trucks or cargo carriers.

The gun, models of 1918 and 1918 Ml is of the built-up type. consisting of a tube strengthened by a ring, jackets, hoops, and the muzzle bell. All details except the firing mechanism provide
interchangeability of parts with the 155-millimeter (G. P. F.) guns A recoil lug on the under side of the breed i of French manufacture.
ring provides

means

of attaching the recoil

and recuperator

rods.

Bronze

clips to serve as guides in the cradle are secured to the sides

of the jackets.

MAXIMUM ELEVATION OF

GUN.

The breech block is
and four threaded

sectors.

of the interrupted-screw type, having four plain The breech mechanism is of the plastic-

obturator type, having the forward mushroom-shaped head of the breech block equipped with an asbestos ring known as the obturator pad. Upon firing, this ring is compressed and acts as a gas check
to prevent the leakage of
sufficient resiliency to
firing

powder gases through the breech. It lias resume its original form after firing. The

mechanism is of the French-percussion primer type described under " 155-millimeter Schneider howitzer/' page 216, and is interchangeable with the guns enumerated therein. The cradle is a steel forging bored with three parallel cylinders for housing the recoil brake and recuperator, and is pivoted by trunnions in the trunnion bearings of the top carriage. On the upper side of the cradle are slots for the gun slides, and to its lower side the elevating rack is bolted
(234)

235

236

237
The
recoil

mechanism

is

of the

hydropneumatic variable

recoil

type. larger of the three cylindrical bores in the cradle block contains the recoil mechanism; the two smaller ones, the parts of

The

the recuperator mechanism. This mechanism consists of a piston and piston rod and a control rod. The piston rod is connected to the breech lug and, therefore,
recoils

with the gun.

Grooves of variable depth are milled along the

length of the control rod, controlling the flow of oil through the The control rod assembles within ports of the piston during recoil.
the bore of the piston rod, and does not
rotates.

move

longitudinally, but

The amount

through which

of this rotating changes the area of the orifices the oil can pass. Its rotation is accomplished as the

gun

is

elevated

by means

of

an arm and gear sectors

in

such a manner

as to shorten the recoil as the

gun

elevates.

CARRIAGE IN FIRING POSITION.

A

replenisher or gravity tank

is

provided in connection with the

recoil cjlinder which assures the recoil cylinders being full at all times and also takes care of any expansion of the oil due to heating.

Its capacity is

about 17 quarts. The recuperator mechanism consists of two connected cylinders, one containing the piston and piston rod which are attached to the breech lug, while the other contains a mushroom valve and a dia-

The diaphragm separates the oil contained in the first and part of the second cylinder from the high-pressure air, cylinder which compels the return of the gun into battery after recoil. Normally a small amount of oil must be between the valve and diaphragm. Oleonapthe is the liquid used in this recoil mechanism. The amount of oil in the recoil and recuperator mechanism is shown by indicators so that it can always be seen whether or not they need filling.
phragm.

238

239
The top carriage is a steel casting mounted on the bottom carriage, on which it pivots to traverse the piece. Belleville springs carry the weight of the gun when traversing, but on firing the springs compress and the firing stresses are taken on the bearing surfaces between the top and bottom carriages. The tipping parts are carried on the trunnions of the top carriage, which also houses the elevating and traversing mechanism and
permits high angle of elevation for the cradle. The bottom, carriage is a steel casting suspended from the axle (in t traveling position) by a heavy multiple leaf spring, supports the top carriage, houses the axle, and provides hinge connections for the trail. When firing the axle is unshackled from the springs and the bottom carriage bears directly on the axle.
j

Traversing is accomplished by rotation of the top carriage on the bearing surface of the bottom carriage by means of a rack and train

ACCESSORIES AND CATERPILLAR WHEEL SHOES.

which are operated by the handwheel on the left side of the A traverse of 60 30 right and 30 left is possible. Elevating is accomplished by a rack on the cradle operated through gears by the handwheel located on the gear box at the left of the top Elevations from to 35 are obtainable. carriage. The trail is of the split type and consists of steel plate beams of box section. Locks are pivoted at the forward end of the trails
of gears

carriage.

them in the open position. When closed together they are clamped and attached to the limber. traveling lock is provided on the trail for retaining the gun in retracted position. Two types of spade are provided, one for soft and one for hard ground. When
for securing

A

traveling the spades are always removed from the trail. The wheels are of cast steel, each wheel having two solid rubber tires and are equipped with the usual band brakes. Caterpillar

wheel shoes for traveling over soft ground are provided, which assemble over the rubber tires. They consist of 12 plates for each wheel, which give a broad bearing surface under the wheel.

18322820

16

240

241
The sighting equipment is exactly the same as that described under the 155-millimeter Schneider howitzer, except the difference in bracket as indicated on page 219.
is of the separate loading type; the projectile 95 pounds and the charge 25 pounds. Either shrapnel or weighs high-explosive steel shell is used, as well as gas shells and other The propelling charge of smokeless powder special ammunition. is a sectionalized charge made up of two sections a base charge and one smaller increment.

Ammunition used

The fuses commonly used are the 31-second combination fuze for use with shrapnel and combining time and percussion elements the point detonating fuze Mark IV used with the steel high explosive shell, and the Mark II point detonating fuze used with gas shell.

155-MILLIMETER

GUN CARRIAGE LIMBER, MODEL
OF
1918

(FILLOUX).

The

carriage limber

is

a two-wheeled vehicle designed to support

and secure the rear ends of the trails and to provide a coupling attachment to the tractor when transporting the carriage. The principal parts are the wheels, axle, steering mechanism, frame, springs, and seat.

The

axle

is

mobiles.
link

It is of

very similar to the usual design of front axles of autoI-beam section, having forked ends with axle arms

pivoted therein, providing a means of steering. By means of a dragand steering lever pivoted at the center of the frame and connected to the steel pole steering is accomplished.

FRONT VIEW OF LIMBER EN ROUTE.

The frame or clamp for holding the gun trail in position is mounted on the axle by means of two semielliptical multiple leaf springs. The upper cross beam of this frame has bolted to it a seat for the brakeman, who operates the gun-carriage brake when en route by means of a lever acting through a wire rope. The wheels are identical with and with the wheels of the gun carriage. interchangeable
Weights and dimensions.

Weight complete Weight with carriage and gun Weight of carriage on limber (traveling

Width of track

position) (center to center of tires)

pounds. do do
millimeters
.

.

3,

23,
6,
.

190 050

2,

Free height under limber and carriage (traveling position) Diameter of wheels Height of seat cushion from ground (seat assembled on top
position)

do
do. ...
of trails, traveling
1,

490 250 250 160
550 500

millimeters.
of carriage axle to center line of

.

1,

Distance from center line on limber)

limber axle

(trails
.

millimeters.
(242)

4,

243

244

6-INCH
r

GUN MATERIEL, MODEL OF

1917 (BRITISH).

n\c 6-inch gun materiel, model of 1917, is British throughout, a being designed and manufactured in England. It consists of Mark XIX, mounted on an 8-inch howitzer carriage, 6-inch gun, Mark VII, known as the 6-inch gun carriage, Mark VIII A. This Mark XIX gun is of wire-wound construction, having a muzzle velocity of 2,350-feet per second and a range of 17,500 yards.
steel wire, jacket, breech

and consists of tubes, a series of layers of bush and breech ring. The breech ring is prepared for the reception of the breech mechanism and is provided with a lug on the under side for the attachment of the hydraulic buffer and recuperator of the carriage. The breech mechanism is operated by means of a lever on the right

The gun body

is

of steel

side of the breech.
is

On pulling the lever to the rear the breech screw unlocked and swung into the loading position. automatically After loading, one thrust of this lever inserts the breech screw and turns it into the locked position. The breech mechanism is similar to that used on the 8-inch howitzers both in design and operation. The firing mechanism is of the percussion type and is not interchangeable with other British guns. The firing mechanism is designed for percussion firing, and is so arranged that the gun can not be fired until the breech screw is locked and the breech mechanism ]ever home. The only changes necessary on the 8-inch howitzer carriages (p. 268) for mounting this 6-inch gun are: The rear extension plug, which connects the gun to the recoil mechanism, is modified and the cut-off
gear
is

of the gun is 8.5 and the distance from the face of the tube to the base of the projectile is 54.39 inches. The volume of the powder chamber is 3,369 cubic inches. The maximum

The chamber diameter

charge consists of 60 pounds of smokeless nitrocellulose powder, which produces the maximum service pressure of 17 tons per square inch. Under these conditions a muzzle energy of 8,315 foot-tons is

CARRIAGE AND LIMBER

IN

TRAVELING POSITION (FRONT VIEW).

imparted to the 153-pound projectile, the muzzle velocity being
2,800 feet per second.

The re coil mechanism is of the hydraulic type; the gun being returned to battery by a pneumatic counterrecoil system. The recoil 'system consists of a simple hydraulic brake, the energy of recoil is absorbed through a distance of 32 inches by forcing a mixture of
;

glycerine and water through orifices of gradually decreasing diameter cut in the head of a piston operating in the recoil cylinder. The method of reducing the size of the orifices is interesting. The
recoil piston

from one

it to allow the liquid to pass the piston starts to move back when the gun is fired. Tapered throttling rods enter the holes in the piston head, and as the piston moves back the size of the orifice is gradThe area of the orifices is so calculated that a ually diminished.

has holes bored through

side to the other

when

constant retardation

is

given to the gun, and
(249)

it is

brought to

rest at

the end of the stroke.

250

mechanism adopted on this mount is similar to mechanism of the French type, as used on 155millimeter guns. In this type of mechanism when the gun is fired, a piston attached to the gun yoke moves backward in an air-tight cylinder containing air at a pressure of several hundred pounds per square inch, still further, compressing the air. The air pressure acting on the counterrecoil piston when the gun has reached the end of the recoil brings the gun back into battery or firing position. The counterrecoil system which is used on this mount is located on the top of the gun, and has been changed into a combination of three The piston cylinders, connected at the lower end by a bronze head. attached to the yoke operates in the central cylinder. The system

The

counter-recoil

the counterrecoil

REAR VIEW OF CARRIAGE.
of liquid packing is retained but simplified and the entire system is of shapes and materials easily secured and is well adapted to

made up

American machining methods.
traversing gear, incorporated in the carriage trail, permits of limited training either side of the center line. When a greater range of training is desired, the trail is either shifted on the ground or the carriage is mounted upon a firing platform which provides for training

A

through a

firing

angle of

60.

A shell-loading

tray,

which

rests

used to load shells into the breech. The elevating gear consists of a simple combination of a handwheel, worm gear, rack and pinion. The sighting arrangements for the gun consist of a standard panoramic field sight fitted to a bracket attached to the gun carriage.
trail, is

on the carriage

251
of the double-tread caterpillar type, is kind of ground designed to carry the mount over practically any The proportions of the chain service. likely to be encountered in tracks are such as to produce a pressure of about 14 pounds per

The track

layer,

which

is

is approxisquare inch upon the soil during transportation, which a horse. The track layer also serves as a mately half that exerted by stand or foundation for the mount during action. A caterpillar tractor is used to draw this vehicle from one position A limber hooked between the mount and the tractor to another. the trail during transit; during action the limber and the supports

withdrawn from the immediate field of danger. The limber wheels are carried on taper axles and are equipped with grease cups for lubricating purposes. A pintle and lunette are provided on the axle in case it is desired to attach an ammunition or supply trailer for transportation. The limber is connected to the
tractor are

LEFT SIDE VIEW OF CARRIAGE IN BATTERY.

mount by means
connection of the

of a swivel pole
trail.

end which

is

pivoted on the limber

The firing platform provides a durable and substantial foundation, adaptable to various soil conditions and light enough to permit of easy and convenient transportation. The firing platform includes a forward table, upon which the track layers rest, and a rear thrust beam to which the trail is secured by suitable pins. The rear thrust

beam

is

made

in

two
is

sections, which,

when combined, provide
section

for

training through an arc of
desired.

Training

One accomplished by
60.

be used alone if shifting the trail around the

may

arc of the platform to the set of pin holes nearest the desired angle. Accurate adjustments in training are made with the traversing gear.

The 7-inch naval tractor mount is so designed that its weight is almost entirely supported by the track layers, but a small percentage of the weight being carried on the trail. When the mount is being pulled along an upgrade of appreciable slope, the center of gravity

252
is

shifted

and the weight
the
air.

of the

gun may have a tendency

to

throw

the

trail in

To preclude any such

occurrence, eyebolts are secured to the

gun

yoke, which are used to draw the recoiling parts back sufficiently to bring about equilibrium. Track grousers may be bolted to the track shoes when there is likelihood of the mount slipping sidewise during transport on hillsides. In an actual road test this gun was pulled over rough ground and proved able to negotiate any ground over which the tractor itself was able to operate. Obstructions were mowed down, and yet the entire weight of the gun was so evenly and well distributed that no damage was done to roads negotiated. The mount functioned perfectly, remaining steady on the point of aim during continued firing. The caterpillar treads, locked in position by the brake, were as steady
as a concrete foundation.

7-INCH
The

GUN MARK

II

AND CARRIAGE MARK
is

V.

7-inch, 45 caliber, naval rifle

built

up

of a tube, hoops,

and

locking rings. When erosion destroys the effectiveness and accuracy of the gun it may be rebuilt by boring out the tube and shrinking in
a conical nickel-steel liner.

weighs 12.81 tons, while the weight of

28,700 pounds. The rifling of 28 grooves and lands, having an increasing twist from zero at the 22 inches from the muzzle. origin to one turn in 25 calibers at a point The remainder of the twist is uniform. This gun is the heaviest and hardest hitting gun for which a mobile lield mount has been requested

The gun, without the breech mechanism, gun and breech mechanism is is right hand of hook section and consists

bv our Army.

CARRIAGE AND LIMBER

IN

TRAVELING POSITION (REAR VIEW).

work

carriage, which supports the gun is a structural steel framebuilt up of standard shapes, consisting essentially of two steel trunnion bearing plates cross braced at each end to form a single

The

unit with a central well into which the

gun

recoils.

These side

girders are riveted to the carriage trail, the carriage and trail forming a rigid unit, are supported on the carriage axle which turns in hubs

mounted

in the truck

the left-hand side of the carriage for elevating and depressing the gun.

On

frames of the track layer. is arranged the mechanism

The traversing gear, which for training 2 either side of the center line, is incorporated in the rear section of the trail. This gear consists of a steel plate resting on the ground underneath the trail: a worm shaft operprovides means
(253)

254
ated by ratchet wrenches shifts the trail with reference to the plate and enables the gun to be accurately trained. Navy guns do not carry the trunnions attached directly to the gun, but are turned to a smooth surface on the outside. The cylindrical gun slide, on which the trunnions are attached, carries the gun; the trunnion seats are placed at the upper end of the carriage. The recoil and counterrecoil mechanisms are also attached to the gun
slide,

operating through pistons atttached to the yoke. The gun runs in and out of the gun slide when recoiling, bronze liners being fitted to the inside of the slide to enable this to take place easily. The trunnions of the gun are mounted sufficiently high so that at maximum angles of elevation only a shallow trench need be dug to permit clearance for the recoil of a gun.

TOP CARRIAGE AND AXLE DETAILS.

The elevating
ting

mechanism,

arc segment, meshing with the pinion of the elevais bolted to a pad on the left-hand face of the slide.

The

teeth of the arc are cut on a pitch circle concentric with the trunnion centers to permit of a 40 movement of the slide in a vertical plane, starting from horizontal. The upper and lower extremities of the arc are fitted with limiting stops to prevent j amming. The hydraulic brake. The energy of recoil is checked and dissipated by means of a hydraulic brake mounted on the bottom of the slide. This mechanism is made up of a piston operating in a cylinder filled with liquid and rigidly fixed to the slide. The piston is attached to the gun yoke by the piston rod which passes through a stuffing box in the rear end of the cylinder. Two orifices are provided in the piston head for throttling rods w^hich are arranged longitudinally in the cylinder. In battery, all the liquid is in rear of the piston. As the piston recedes during recoil, the liquid is forced around the throttling rods through the orifices in the piston to the forward end

255
of the cylinder, dissipating the erffergy through the frictional heat generated. The cross section of the throttling rods, around which

the liquid must flow in passing through the orifices, is such that a pressure approximately uniform is exerted upon the liquid throughout the period of recoil. The length of recoil is 32 inches.
.

Incorporated in the cylinder head is a counterrecoil chamber into which the recoil liquid flows during recoil. When the gun is brought back to battery by the counterrecoil mechanism, its momentum is

ASSEMBLED VIEW OF HYDRAULIC BRAKE.

checked through the action of a counterrecoil plunger, mounted on the forward face of the piston, as it enters the chamber and forces
the liquid back into the cylinder through the orifice between the plunger and the plunger bushing screwed into the mouth of the chamber. This action takes place during only the last 14 inches of counterrecoil stroke.

The

liquid used in the hydraulic brake consists of a mixture of 4

parts glycerine and 1 part water, by volume. This liquid is poured into the cylinder through a filling hole on the right-hand side of the
cylinder head.

18322820

17

256

The upper portion of the cyliiuter head is arranged to form an expansion chamber to provide for the expansion of the liquid which results from the f fictional heat generated in the cylinder. When expansion of the liquid takes place with continued firing, the increased volume of the liquid simply compresses the air in the expansion chamber instead of acting to prevent the return of the gun to battery. To assure the presence of a definite amount of air in the expansion chamber at all times, the filling hole is fitted with a tube which extends down into the chamber and traps the desired volume of air when
the cylinder
is filled.

Counterrecoil system. Energy to return the gun to battery and to maintain it in that position at all angles of elevation is obtained by

means

of a

pneumatic counterrecoil system, mounted on the top

of

VIEW OF AXLE MOUNTED
the
slide.

IN

TRACK LAYER.

A

the gun yoke

by

piston, operating in an air cylinder and connected to a piston rod, serves to compress the air within the

cylinder when the gun recoils. At the end of recoil, the compressed On either side air acts upon the piston to return the gun to battery. with it through a port is an air tube of the air cylinder and connected

which serves as a
Since
it

reservoir.

necessary for the counterrecoil system to support the of the gun and breech mechanism against gravity, the system weight is charged initially with air at 300 pounds per square inch, gauge presThis pressure assures the proper functioning of the countersure. recoil mechanism at angles of elevation up to approximately 34. It is apparent that the factor of gravity decreases with the angle of elevation and hence less pressure is required to bring the gun to batis

terv

when

it is

fired at angles

near horizontal.

257
charged to 340 pounds pressure, the mechanism will function properly at all angles; however, if the cylinder should be charged only to, say, 225 pounds, the mechanism may be relied upon to return the gun to battery at angles of elevation up to 23 or 24. To insure return of the gun to battery when firing at angles above 34, air cylinders should be charged in accordance with the instructions, and to prevent breakage of the gauge glass and to preserve the accuracy of the instrument, it is recommended that the pressure gauge be

When

removed before
on the

firing.

The elevating gear train from the rack on the
left side of

the
arc.

trail is

made up
of

with the elevating

One turn

handwheel and shaft in mesh the elevating handwheel moves
slide to the

of a pinion

the gun 56' 17" in elevation or depression. The axle, a steel forging extending across the width of the carriage is supported in the track layer by a hub bracket which in turn is carried by the structure of the girder on which the sprocket and truck

L
SIDE ELEVATION OF

TRACK LAYER.

wheels are mounted.

This bracket is held by oscillating bearings spring supported so that the caterpillar may adjust itself to unevenness in the road when the gun is in motion. When the any gun is placed in firing position, the springs are taken up by means of holding down screws in order that the mount may keep steady on the point of aim while firing. The function of the hub springs is to impart to the mount a degree of resiliency during transit. However, when firing, resiliency in the mount is undesirable and often dangerous, thus before firing the springs are compressed until the hubs bear directly upon the truck frames. This is accomplished by means of adjusting screws screwed down on the hub bearing blocks until the springs are compressed and the hubs rest solidly upon the truck frames. The trade itself consists of an endless belt of cast steel links connected by hardened pins, each link carrying a corrugated forged-steel plate which makes contact with the ground. The plates overlap when horizontal so that a continuous surface is presented. To prevent the

and

is

258
corrugated surface of the tread from slipping in soft ground, detachable grousers are provided. The track links run over a large idler wheel, a sprocket wheel, seven truck rollers, and four track rollers on each caterpillar track The sprocket wheels carry but little of the load except when layer. the gun is descending a grade or when the brake is applied to the

mount.

For smooth running and reliability, roller bearings are fitted in the truck and idler rollers, the ends of the rollers being closed by
steel plates to

prevent the entrance of dirt when the mount is hauled through mud, sand, or soft earth. A brake is provided to permit control of the mount when descending hills and also to lock the caterThe brake conpillar in position when the gun is set up for firing. sists of a toggle joint operating on the rim of one of the sprocket
wheels, the tension applied being controlled

by an adjustable

spring.

CARRIAGE IN BATTERY POSITION, SHOWING MAXIMUM ELEVATION OF GUN.

Simple as the brake

has been exceedingly satisfactory in operaheavy mount on steep grades and in checking any tendency of the mount to move on firing. The track is carried around two track idler wheels which are provided with bearings mounted on the extremities of the track frame. The aft idler wheel bearings are so mounted that they may be moved backward or forward as necessary to adjust the tension and to take up wear on the links and shoes.
is it

tion in controlling the

Friction brakes operating against the forward idler wheels

are

mounted on the truck frames. These brakes are of the spring release type and are applied by means of handwheels functioning through yokes and levers to the brake shoes. The quadrant sigJit (Schneider} is mounted on the left trunnion of
the carriage both in traveling and in action.

8-INCH HOWITZER MATERIEL (VICKERS).
Success has been obtained with the 8-inch howitzer artillery for preliminary bombardment which precedes an infantry attack. This

mobile in a sense, but there are limits to its mobility, for When these a time when its advance must stop. howitzers have to be transported over land full of huge craters r with the roads entirely destroyed, the country encumbered with all kinds of debris and frequently reduced to a sea of mud, it can be
caliber
is

there comes

easily seen why a successful "push" usually nets a considerable gain in captured artillery. If the trenches give way, it is almost

impossible to get the heavy howitzers

away quickly enough

to save

CARRIAGE IN BATTERY POSITION.

is

them from being captured by the enemy. Thus, by mobile artillery meant that which can be moved around essentially as part of the

infantry.

The howitzer, being comparatively thickset and short when compared with a gun of the same .caliber, is capable of greater angle of elevation than the same caliber of gun. The gun is primarily intended for attacking troops, while the chief aim of the howitzer is to destroy incumbrance such as trenches, barbed wire, pill boxes, and the like. A shell that travels from the howitzer ascends at a high angle and drops almost vertically. The explosion of a shell so fired is much more effective than one that is fired with only a slight
elevated trajectory, as in the case of the field gun.
(259)

260

261

The 8-incli howitzer, being mounted on a wheeled carriage and not having to he disassembled for transportation, is much more mobile than the 9. 2-inch or 240-millimeter howitzer. This howitzer when set up ready for firing rests on and is braced upon a firing platform, which is transported on a two-wheeled wagon, the wagon being attached to the howitzer carriage and drawn as part of the unit with the carriage and limber by a tractor. On reaching the spot selected for position the firing platform is buried flush with the
surface of the ground, furnishing a steady
to
fire.

emplacement from which

The 8-inch howitzer materiel is called the "Vickers" model of which there are in use two types, the Mark VI and Mark VII. The main differences between the Mark VI and the Mark VII being that the former has a lower muzzle velocity and consequently a shorter range than the latter, also that the Mark VII has a barrel of the "wire wound" construction, whereas the Mark VI type is of the "built up" construction. The Mark VII is also longer and heavier
1917, of

than the Mark VI. The Mark VII has lately been superseded by a Mark VIII^, the difference between the two being that the powder chamber walls of the Mark VII proved to be too thin, while the Mark VIII^ overcomes
this defect

by having thicker powder chamber

walls.

Due

to the

fact that the

Mark VIIIJ howitzer has

a greater muzzle velocity,

and consequently a greater maximum range than the Mark VI by some 15 to 20 per cent, the former is the preferred type. The life of the howitzers before relining is necessary varies greatly. 'Hie number of rounds they are capable of firing before the lining becomes badly worn depends on whether light or heavy propelling charges are used. The use of light propelling charges and greater trajectory elevation to get the desired range is recommended rather than heavy charges and low elevation. From information based on
is

actual experience the average life of the 8-inch howitzer, Mark VI, 7,800 rounds, while that of the Mark VHIi is 3,000 rounds.
hoivitzers,

Comparative table of weights, dimensions, and ballistics for 8-inch and Vlin and 6-inch gun, Marie XIX.

264 The elevating mechanism permits a movement of 50 maximum elevation for the Mark VI carriage, 45 for the Mark VII carriage, and 88 for the Mark VIIIA carriage.

The

cradle pivots on its trunnions

in the top carriage,

which

in turn is

rests in bearings provided pivoted at its front center to a
it is

and

transom on the trad in such a manner that

free to rotate

under

REAR VIEW OF CARRIAGE, SHOWING MAXIMUM ELEVATION OF HOWITZER.
control of the traversing gear, 4 to the right or 4 to the left of the center line of 'the trail, a total of 8 traverse for each of the three
types.

quick-loading gear is fitted to the cradle for bringing the howitzer rapidly to the loading position (7 30' elevation) after firing, and vice
versa.

A

The trail is composed of two side members supported at the front end of the axle and terminating in a spade at the rear end. Screw
ward end
brakes for use in firing or traveling are fitted to either side at the forof the trail. A traveling lock is provided on the trail to lock the trail and cradle

together to prevent strains on the elevating and traversing mechanisms when traveling.

265

The wheels

are

made
is

entirely of steel

and have wide

1

ires fitted wil

li

steel cleats to ensure

good traction.

The

sighting gear

sight and clinometer

for the usual

composed of a rocking bar sight with panoramic, method of sighting and a dial sight

266
These types of carriages are provided with a platform by means of which a traverse of 26 right and 26 left is obtainable. The platform is used whenever conditions and time permit emplacement. For transportation the platform is disassembled and placed- on a transport wagon, which consists of two wheels and an axle, to which
the parts of the platform are securely clamped. Eight-inch howitzer materiel (British) consists of: Model of 1917 (Vickers Mark VI and Mark VII). Model of 1918 (Vickers Mark VII).

model of 1918 (Vickers Mark VII). Howitzer, model of 1918 (modified from Vickers Mark VIII to United States Mark VIIIJ). Limber, model of 1917 (Vickers). Firing platform and wagon, model of 1917 (Vickers). The above materiel is of British design and of both British and American manufacture.
Carriage,

267

B

* s

I

s

8-INCH HOWITZER

AND CARRIAGE

(BRITISH).

consists of a tube over

The Marie VI howitzer is of the built-up-construction type and which is shrunk a jacket. Front and rear

guide rings provide means of supporting the howitzer in the cradle. A breech ring is also shrunk on for additional strength and carries a lug for connecting the gun to the recoil mechanism, and a breech bushing is provided for reception of the breechblock. The total length of this howitzer is about 10 J feet and its maximum range is approximately 10.760 yards; this howitzer is mounted on the Mark

VI

carriage.

REAR RIGHT SIDE OF CARRIAGE

IN FIRING POSITION.

The Mark VI11$ howitzer is also of the built-up-construction typo, but differs from the Mark VI howitzer in that it consists of two tubes, an inner and an outer, over which is shrunk the jacket. The jacket in this case supports the howitzer without the use of guide rings. A breech ring is shrunk on over the jacket and carries a lug for connecting the gun to the recoil mechanism. A breech bushing similar to that of the Mark VI is fitted for the breech mechanism. The total of this howitzer is about 12 i feet and its maximum range is length approximately 12,360 yards. This howitzer is mounted on the Mark

VII

carriage.
(268)

269

270

271
It is operated is of the interrupted-screw type. a lever on the right-hand side of the breech, which by one motion by releases the screw threads and opens the breech, or vica versa, on
closing.

The breechblock

The forward mushroom-shaped head of the breechblock is equipped with a flexible asbestos ring, known as the obturator pad. On firing, this ring is compressed and acts as a gas check to prevent the leakage of powder gases back through the breech. It has sufficient resiliency to resume its original form after firing, as described on page 216. For firing the charge, two separate types of igniters or primers are The one known as the T tube consists of a. small T-shaped used. copper tube which fits into a suitable socket in the breech; it is fired by pulling a friction wire out of the tube by means of a lanyard. The

BREECH BLOCK.
other type, the percussion primer, is very similar in construction to a blank rifle cartridge. It fits a percussion firing mechanism on the breech which fires the primer by means of a hammer operated by the lanyard. This mechanism is common and interchangeable with the
155 millimeter gun and howitzer; also the 240 millimeter howitzer. Howitzers fitted for one type of primer will not permit the use of the other type. Both types have a safety lock, which prevents
is not entirely closed. mechanism is of the hydropneumatic long-recoil type and contains both recoil brake and recuperator. The recoil mechanism is an hydraulic brake to absorb the energy of recoil of the piece. It consists of a piston rod and piston traveling in an oil-filled cylinder. The piston rod is connected to the cradle 18322820 18

firing

when

the breech

The

recoil

272

273
which remains stationary while the howitzer recoils. 'Die cylinder block is connected to a lug on the howitzer and recoils with it so that
the gun is fired the piston is forced against the oil in the cylinder. Ports are provided in the piston to permit of the passage of some of the oil. At the beginning of the recoil a large quantity of oil is permitted to pass, but as the howitzer further recoils a valve on the piston rod, operated by lugs sliding in spiral grooves in the cylinder walls, gradually closes the port so that no oil can pass and the howitzer is

when

brought gradually to

rest.

FRONT VIEW OF HOWITZER CARRIAGE.
In order to prevent the gun striking the ground when firing at high elevation, a method is provided for automatically closing the piston valves sooner as the elevation increases, thus shortening the
recoil.

The mechanism which accomplished

this feature is

known

is extended and so designed that it forms a counterrecoil buff er when it enters a suitable chamber bored out in the buffer plug. This buffer prevents violent return into

as the valve turning gear. The rear end of the piston rod

firing position after recoil.

The recuperator or counterrecoil mechanism serves to return the howitzer to firing position after recoil. It consists of two liquid cyl-

274
inders which are connected in turn with two air cylinders.

On recoil-

ing, the recuperator pistons force the oil out of the recuperator cylinders into the air cylinders, thereby highly compressing the air.

When

this air

expands

to its original

volume

it

drives the

oil

back against

position.

the recuperator pistons, thereby returning the howitzer to firing The recuperator also acts as an auxiliary recoil buffer, absorbing up about 10 per cent of the energy of recoil. The air in

the recuperator is maintained at a pressure of about 700 pounds per square inch in order to prevent the howitzer slipping back on the A suitable pump is provided with the matecradle at high elevations. rial for maintaining this air pressure.

ELEVATING AND TRAVERSING MECHANISM.

The carriage consists
axles,

of a top carriage, cradle, trail,

wheels with

and the elevating and traversing gear. The Mark VI and Mark VII carriage are similar in design and differ only in that Mark VII has a slightly larger recoil mechanism and the trail is cut out somewhat to allow for the greater length of the howitzer recoil. The top carriage is built up of nickel-steel plate and carries the trunnion bearings for the cradle. It is pivoted in the front transom
of the trail, so as to permit the necessary traverse. The cradle which carries the recoil mechanism and provides slide ways for the recoil of the howitzer when in action, is supported by

the trunnion bearings of the top carriage.

275

276

277
The trail is of the solid type, cut out to provide clearance for the howitzer to recoil. The spade is removable and the shoe or bracket may be substituted when firing on scotches or using the firing platform.

The elevating and traversing gears are operated by handwheels on The Mark VI carriage permits of an the left side of the carriage. elevation of 50; the Mark VII, 45; and the Mark VIII-A, 38. Both carriages permit a traverse of 8.
quick-loading gear is provided to allow the gun to be brought rapidly to loading position when firing at high angles of elevation. The wheels are ol the all steel wide- tire type, 66 inches in diameter

A

with

tires 12

inches wide.

They

are fitted with brakes which act

independently on each wheel. Sighting is accomplished by means of a rocking-bar sight supplemented by a panoramic sight. These are located on the left SKU
*.>

A

the piece and serve to lay for elevation and traverse respective^. dial sight is provided on the right side of the piece for quick laying. Ammunition of the separate loading type is used with the 8-inch

Shell issued is of the high-explosive type only and weighs howitzer. 200 pounds. These are issued filled but not fuzed and are fitted with a booster and adapter. Fuzes of types to suit different conditions of firing are provided, giving delayed or instantaneous action. The propelling charge is contained in cloth bags and is made up of separable increments, permitting various zones of fire. The maximum charge for the Mark VI howitzer weighs 10.8 pounds; for the

Mark Vlllf

howitzer, 17.5 pounds. Separate loading ammunition is used in the 6-inch gun mounted on a Mark VIII-A carriage. The original British ammunition so closely resembled the American that it was decided to use the regular Mark II high-explosive shell. Each round is issued with the projectile filled, also the adapter and booster in place. The fuze hole in the adapter is fitted with a white metal plug. The weight of the

The propellant charge will projectile complete is 90.33 pounds. consist of a base section and increment section having a total weight
of approximately 25 pounds.

8-INCH HOWITZER CARRIAGE LIMBER,
1917

MODEL OF

(VICKERS).

The limber provided with this and for the 6-inch gun materiel is of and provides a chest for tools and spares, also seats No ammunition is carried in this limber, but two for the personnel.
steel construction

types of poles are provided, a long one for horse-drawn vehicles and a shorter connecting pole for motor traction. The box or chest of limbers manufactured in England is of wood and is bolted to the top of the rails. The lid is covered with water-

proofed canvas and hinged at the front. Those limbers which were manufactured in the United States are provided with steel chests which vary slightly from the wooden chests in fittings provided for
tools

and accessories. The axle is cylindrical

It passes

and fitted with special axle arms. formed in the rails and is held in position through bearings
in shape
is

equipped with guard irons and blanket straps, receptacles being provided on the sides and ends to take an The interior of the chest is fitted ax, a shovel, and other implements. to carry tools, spare packings for buffer and recuperator, and other
necessary stores.
Clips are secured at the front of the chest to

by brackets. The top of the chest

accommodate two rifles, used in emergencies when attacked en route. The wheels are 66 inches in diameter and have a tire 6 inches in width with rounded edges.
Weights and dimensions.

wooden firing platform is provided on which the carriage of the 8-inch howitzer and 6-inch gun materiel can be mounted when sufThe platform consists of ficient time is permitted for setting up. wooden beams which assemble to form a triangular platform. The
spade must be removed and a special bracket fitted on the trail when using this platform. This bracket travels in a groove which gives a bearing for the bracket and also provides a means of traversing the piece 52 on the platform. The platform is disassembled and mounted on a pair of wheels and axle for transportation.

The main objects in the use of the firing platform are: To provide a reliable suppport for the wheels and rear end of the trail, so as to prevent sinking or movement when firing on soft ground; to insure
the

gun remaining on the

target

when

firing;

and

to provide

means

for shifting the trail transversely through an angle of 52 (26 each side of center). By using the traversing gear on the carriage a total traverse of 30 on each side of the center is obtainable.
is composed of a support upon which the wheels two side beams hinged together at the forward of the carriage rest, end and a rear beam made in a top and bottom section. These components form a triangular-shaped frame upon which the carriage

The

firing

platform

may

be placed

when

firing.

for the carriage wheels is placed near the apex of the formed by the hinged side and rear beams. The rear beams triangle form the base, the upper one being curved at its front edge to form

The support

a guide for shifting the trail. The carriage wheels rest on steel plates on the wheel platform and are guided by curved-steel angles which

prevent lateral movement of the gun off the target when in -action. When the firing platform is used, the float plate, with spade attached, which is bolted to the underside of the trail, is removed and another float plate, having a thrust bracket attached, is bolted in
its place.

In traveling the units of the 8-inch materiel are arranged in the following order: Limber, carriage, and platform wagon. The usual plan is to draw this combination by a tractor.
(281)

mobile type in service by the American Army at the present time. While these calibers are mobile in a sense, yet there are limits to their mobility, for when these howitzers have to be transported over land full of huge craters, with the roads entirely destroyed, the country encumbered with all kinds of de*bris, and frequently reduced to a sea of mud, one can realize just why a successful attack usually
nets captured artillery, and on the other hand, if the trenches give way, it is rather difficult to got these heavy howitzers away quickly enough to save them from being captured by the enemy. Both types of 9. 2-inch howitzers are practically similar in all

both being platform mounts as illustrated. These units break up into three separate loads for traveling, the howitzer proper forming one load, the top carriage and cradle the second load, and
features,

the platform the third load.

The Mark
type
is

I type of howitzer is 13 calibers long, while the Mark II 17.3 calibers, the principal difference being that the latter

model is a more powerful weapon. Both types are provided with an earth box which is secured on firing beams, and in which the earth excavated for the firing beams is thrown; the additional weight gives
greater stability

when firing. The recoil mechanism is of the variable type which limits the amount of recoil according to the elevation, the recoil cylinder being
with a counterrecoil buffer to control the return of the howitzer

fitted

into battery. gravity tank insures that the recoil cylinder will at all times be filled with oil, but will provide the proper amount of

A

void for expansion of the

oil

The

counterrecoil

mechanism

in the cylinder. is of the pneumatic type consisting

of a cylinder, a piston with rod,

and a

floating piston.

The

floating

piston separates the oil and air chamber and the rod extending through the oil chamber provides a differential pressure and effects a seal, preventing the air leaking into the oil chamber.

The operation of the howitzer in firing is that the recoil cylinder and the counterrecoil, or recuperator piston rod, move to the rear with the howitzer, the recoil piston rod and the recuperator cylinder
remaining stationary. The flow of oil in the recoil cylinder past the piston rod and valve limits the length of the recoil and the compression of the air in the recuperator cylinder
(283)
is sufficient

to return

284

285
it

to battery after the force of the recoil has

been absorbed.

The

counterrecoil buffer in the recoil cylinder limits the counterrecoil of t he howitzer and allows the piece to return to battery position with-

out shock.

The howitzer, being comparatively thickset and short when compared with a gun of the same caliber, is capable of greater angle of

FRONT VIEW SHOWING MAXIMUM ELEVATION OF HOWITZER.

same caliber of gun. The gun is primarily intended for attacking troops while the chief aim of the howitzer is to destroy incumbrance such as trenches, barbed wire, pill boxes, and the like. A shell that travels from the howitzer ascends at a high angle and drops' almost vertically. The explosion of a shell so fired is much more effective than one that is fired with only a slight elevated trajectory as in the case of the field gun of the same caliber.
elevation than the

286

From information based on actual experience, the 9.2-inch how-, itzer, Mark I type (low velocity), has an average life of 8,300 rounds, while the Mark IT (high velocity) has an average life of 3,500 rounds.
The howitzer transport wagon
of
is

a four-wheeled vehicle the body

which contains a winch for removing and mounting the howitzer This vehicle is equipped for motor traction and has in the cradle. brakes acting individually on each hind wheel. The carriage bed (or platform) transport wagon is formed by fixing a front and rear axle to suitable attachments on the bed, thus forming the body of the wagon. Attachments are provided for brakes which act independently on each hind wheel and connections for attachment behind the howitzer transport wagon.

LOADING POSITION OF HOWITZER, SHOWING SHELL ON TRAY.

The top carriage transport wagon is formed by attaching two axles with wheels to the top carriage, which forms the body. Individual brakes are fitted on the hind wheels. This vehicle is usually coupled behind the platform wagon. The three wagons are drawn en train by tractor but may be hauled
singly in case of necessity.

This materiel is designed to be transported in separate loads, thus three four-wheeled vehicles are issued for this purpose. The first carries the howitzer, the second the carriage, and the third the
platform and earth box, all of which is of British design, but the United States is in possession of equipment made both in this country and Great Britain.

REAR VIEW OF CARRIAGE, SHOWING HOWITZER AT MAXIMUM ELEVATION.

The howitzer consists of a tube, muzzle stop ring, a series of layers of steel wire, jacket, breech bushing, and breech ring. Over the exterior of the tube is wound a series of layers of steel wire extending from the breech end to the stop ring, which is shrunk over the tube

Over the exterior of the tube is shrunk the jacket, secured longitudinally by the breech bushing. The bushing is prepared for the reception of the breechblock. The breech ring is screwed and shrunk over the jacket at the rear.
at the' muzzle.
is

which

(288)

The Mark
other,

II

differs in that
is

it

on which (he wire

wound.
II

has two tubes shrunk one over the The Mark 1 howitzer is 133
is 17()

inches in length, while the

Mark

inches.

The breech mechanism of the screw type with plastic obturator is so arranged that by partially revolving the operating lever the breechblock is unlocked and the block with the gas-check pads and disks withdrawn from the seating in the chamber. The breech mechanism can then be swung into the loading position by means of a handle on

The breech is closed by a parallel the rear face of the breechblock. screw having five portions of the screw thread removed longitudiThe main characterisnally, each one-tenth of the circumference. tics of the Vickers 9. 2-inch howitzers are indicated in the accompanying table, giving the important dimensions, weights, and ballistics.
I breech requires two operations to open. A handle on the rear of the block revolves and releases the block, then turning

The Mark

BREECH MECHANISM (MARK
it

I).

Mark

must be swung open by the handle provided on the breech. The II breech can be opened by one motion of a lever on the right

side of the breech,

which revolves and withdraws the breech in one motion from front to back. Both types are fitted with a firing mechanism to accommodate the T-tube primer. Later models are fitted with the French percussion type of firing mechanism described with the 155-millimeter howitzer
materiel
011 page 216. The recoil mechanism is of the hydropiieumatic type and is equipped with a variable recoil, which shortens the length of recoil after 15

elevation.

The recoil cylinder is located above the howitzer, the former beingsecured to the howitzer and moves with it, while the piston rod is secured to the cradle. The recoil is controlled by passage of oil
through ports
in the cylinder,

which are varied by the valve located

290
near the piston on the rod. This valve is rotated by lugs which engage spiral grooves in the cylinder. A mixture of glycerine and oil Later models are fitted with gravity tank is used in the cylinder.

on top of the recoil cylinder to replenish the oil and relieve pressure due to expansion. The end of the piston rod is extended and shaped to form a counterrecoil buffer. The recuperator is located below the howitzer; the cylinder being secured to the cradle remains stationary when the howitzer is recoilThe ing; but the ram is secured to the howitzer and moves with it.

ram on

separated by a floating piston. The increases the liquid pressure on thi& piston this in recoiling turn compresses the air, which on expansion will return the howitzer
oil

and

air in this cylinder are

;

to battery.

An

initial pressure of

maintained in the

air

475 pounds per square inch chamjber to hold the piece in battery.

is

RETAINING CHTCH

BREECH MECHANISM (MARK

II).

To maintain this pressure a pump is attached to the carriage, which can be operated either by hand or a small gasoline engine. The cradle is a cylindrical chamber formed to house the howitzer. It is provided with trunnions and has the elevating arc secured to its lower side. Grooves cut in the cradle cylinder serve to guide the howitzer during recoil. A toothed arc on the left trunnion operates the valve turning gear through gearing. The top carriage or body is built up of steel plates. A front transom carries the pivot block, which fits over the pintle on the bed and on which the top carriage pivots. To the rear transom is secured a pinion which, meshes with a rack on the bed, serves to traverse the
piece.

Suitable platforms are hinged to the body, thus permitting

access to working parts and loading platform on the rear for the perOn the left rear side of the body is a loading gear, which *sonnel.
consists of a swinging

arm with

a winch and loading tray.

291

292
The traversing gear is actuated by a liandwheel on the left side of the carriage, motion being transmitted to a vertical rack pinion which works in the rack at the rear of the bed thus a traverse of 30 right
:

and

left

may

be obtained.

METHOD OF LOADING, SHOWING LOADING GEAR MECHANISM

IN ACTION.

The elevating gear is operated by a handwheel on the left side of the carriage, which, through a system of gearing, operates the arc beneath the cradle.

RIGHT SIDE VIEW OF CARRIAGE

IN BATTERY.

quick-loading gear operated by a handwheel on the right of the carriage permits the howitzer to be brought readily to the loading The firing angle ranges from 15 elevation to angle, 3 depression. 55 elevation.

A

293

294

295
The bed on which the top carriage pivots consists of two steel side guides of box section with transom, a pivot block, and a travThe bearing of the top carriage is formed by an upper ersing rack.

and lower

roller path.

At

the front of the bed are suitable connecis filled

tions for fastening a steel tain stability.

box which

with earth to help main-

Sighting is accomplished by means of a rocking-bar sight, a panoramic sight, or a No. 7 dial sight located on the left of the carriage.
sight serves to lay for elevation and carries the The dial telescope sight or the dial sight for laying for direction. is similar to the United States panoramic sight, which can be sight

The rocking-bar

substituted.

Ammunition employed
explosive steel shell

the separate-loading type. Highweighing 290 pounds are used, which are fitted
is

of

with percussion fuses. The propelling charge is put up in cloth bags, charges being built up with four and with five increments for zone fire are provided. The charge is ignited by the T-tube friction type of primer.
Weights, dimensions,

and

ballistics.

Mark
Weight
Weilit

I.

Mark

II.

of howitzer

without breech mechanism

pounds..

of howit er with bree>

h me< hanism

do
inuhes.
.

Total length of howitzer Rifling (uniform). Powder haree
i

9,576 170J
27 290 1,500 13,080

pounds.
ft.

.

Weight of shell
Muzzle velo"ity

Maximum ranre

do.... per sen. yards. .
.

Wei< ht of mount in firing position complete with howitzer (but without dirt in earth box) pounds. Weii h t of body and Cradle do Weirht of bed and earth box do Wei'ht of earth box empty do Woii ht of firin<r beams do Wei' ht of eround ramps do inches. Length of recoil at 15 elevation Leneth of re'-oil at 50 elevation do

2SO 1,187 10,060
100 10,100 8, TOO 1,600 4,200 410 40
'29,

.

35,500 11,200 9,100 2,100 5,700 530
44 19

.

Maximum angle of elevation
of traverse.
. .

degrees .

.

19 50

50
3

Amount

Loading anele (depression)
. .

do
.do.
. .

9.2-INCH

HOWITZER TRANSPORT WAGON

(VICKERS).

This wagon consists of a front and rear axle and a steel rectangularbed prepared for transporting the howitzer. The front axle is of forged steel, having an axle arm on each end, The to which are fitted 60 by 6-inch steel tired wooden wheels.

framework is formed for the reception of the axle and draft pole, and has provisions for the attachment of a tractor. The bed for transporting the howitzer is prepared on its upper surface to receive the howitzer and is supported at the rear on an axle, each axle arm being provided with a dust excluder and linch When traveling the front end of the howitzer is secured by pin. pawls; the muzzle end being supported by two bronze brackets arid
steel

METHOD OF MOUNTING HOWITZER.
secured by a wire rope and draw nuts. The frame is fitted with a draft link in rear for attachment of the draft connector of the next
load.

purpose of shifting the howitzer into, or from, provided consisting of an endless chain which, by means of sprocket wheels, imparts motion to a larger endless chain to which the howitzer is connected. Two rods, one on each side, are secured to a crossbar for connectthe cradle
is

A winch gear for the

ing the rear of the wagon to the carriage body dismounting the howitzer.

when mounting

or

The brake gear consists of two brake arms and brake screw fitted with handwheels and two brake blocks. Each side is operated independently by handwheels from the rear. A roller scotch and drag shoe, connected by chains, are attached for use when traveling.
(296)

297

298
Weights and dimensions.

299
9.2-INCH

HOWITZER PLATFORM TRANSPORT WAGON

(VICKERS).

The howitzer platform-transport wagon
to the howitzer carriage-transport wagon. connections are entirely similar to those

in general is very similar

The front axle and draft on the howitzer carriage-

transport wagon, except that only one hole in the center of the axle When preparing for travel the is provided for the raising screw.
rear axle, which is fitted with two vertical holes for lifting screws, is attached to rear of the bed. The axle is fitted with dust exchider, linch pins and adjusting collars, and a brake gear which is operated

from the rear by handwheels, each side being operated independently. The roller scotch and drag shoe are similar to those used wath* the
howitzer carriage- transport wagon.
Weights and dimensions.

240-MILLIMETER HOWITZER MATERIEL, MODEL OF
1918

(SCHNEIDER).

The 240-millimeter howitzer unit, a French design translated to accommodate American manufacturing practice, differs from the smaller type of field artillery pieces in that it is split up into a number

When arranged for firing the carriage is set of loads for transport. a structural-steel platform which rests in a special prepared pit upon and has a large trunk portion embedded in the ground to absorb the
reaction of the recoiling parts. hinged floats at the rear.

The platform

is

stabilized

by two

FRONT VIEW OF CARRIAGE, SHOWING MAXIMUM ELEVATION OF HOWITZER.

Although approximately the same
itzer (the exact

size as the British 9.2-inch

how-

diameter of the bore of the 240 being 9.45 inches) and only a little larger than the 8-inch howitzer, the French gun is by far more powerful than either. The 8-inch and 9.2-inch howitzers have ranges in the neighborhood of 6 miles, their shell weighing 200 and 290 pounds, respectively. On the other hand, the 240 hurls a shell weighing 356 pounds and carrying a bursting charge of 45 to 50 pounds of high explosive, obtaining a range of almost 10 miles. It is-estimated that the life of the 240-millimeter howitzer before relining is approximately 5,000 rounds.
(300)

301

302

303
Comparative
characteristics of heavy artillery.

304

composed of a limber, false trail, and a rear two-wheeled wagon. and accessories for each unit are carried on two 4-ton trailers and the six loads are drawn by caterpillar tractors. In assembling and dismounting, an erecting device made of structural steel is used for placing the platform and top carriage in position. The cradle and howitzer are drawn into place by a cable and windlass which is attached to the forward part of the top carriage. This erecting device is also used for lifting and placing projectiles on the shot truck from the shell storage. The howitzer, when elevated to about 43 J and using a propelling
unit
is

The

tools

charge of 35 pounds, giving a pressure of about 33,000 pounds per square inch on the base of the projectile, will fire a projectile weighing 356 pounds and containing a bursting charge of about 49 pounds of T. N. T. to a distance of approximately 10 miles.

METHOD OF LOADING THE HOWITZER WITH RAMMER

CAR.

The following sighting equipment materiel
:

is

carried with the 240-millimeter

Quadrant sight, model of 1918. Panoramic sight, model of 1917.

Peep

sight.

Sight extension. Gunner's quadrant, model of 1918.

Night lighting equipment for

sights.

used with this howcommon-steel shell itzer, and point-fuzed gas semisteel shell. The shells are issued filled but not fuzed, the fuze hole being closed with a suitable plug. The components of each round are the primer, the propelling charge, the
of the separate loading type is consisting of point-fuzed high-explosive
filled projectile,

Each transport vehicle consists principally of a limber, and rear axle and wheels. The limber consists of wheels, axle, pole, and turning

faJse trail,

arc

and

is

It is equipped with a pintle, over which similar for each wagon. The turning arc is attached fits the lunette ring of the false trail.
to the axle,
pintle.

and the

false trail bears

on

it as it

rotates around the

fitted at the front

are provided, one for -each wagon. They are end with a lunette ring and at the rear with a locking arrangement for attachment to the unit to be transported. The rear axles are provided with suitable means for attachment to their respective units, and band brakes are fitted on all the rear

Four

false trails

axles.

When the complete carriage is set up for firing, the transport vehicles are close coupled by means of the false trail and form short All wheels units, having four wheels, which can be drawn away.
are equipped with solid rubber tires.

The howitzer is built up of alloy steel and consists of a tube, a The jacket is shrunk on the rear end of the tube jacket, and hoop. and is secured from slippage by threads cut in its inner surface, which screwr over corresponding threads on the tube, the rear end The of which is prepared for the reception of the breechblock. is shrunk and screwed on the tube forward of the jacket, which hoop is fitted at its rear end with a hinge lug, vertical clips for joining the howitzer to the sleigh, and guide bosses for joining the sleigh to the
howitzer; also a T slot to suit the false trail when entrain. At the front end of the hoop is a boss to accommodate the axles of the transport wagon and lugs for rollers used in the dismounting and

mounting of the howitzer. The breech mechanism is
fitted

of the interrupted-screw type and is with a plastic obturator. One motion of the breech lever swinging from left to right turns and swings the breech clear.

308

The
the

firing

as used

mechanism is of the French percussion type, the same on the 155-millimeter howitzer, and is interchangeable with
of the following materiel:

The sleigh, a steel forging, is bored out to house the recoil mechanism and supports the howitzer, being attached to it by lugs and locking clips, and therefore recoils with the howitzer when in action. Grooves in the sleigh house guides fastened to the cradle which The sleigh is also fitted with serve to guide the howitzer in recoil. on the howitzer, which are used in mounting two tracks for the rollers and dismounting. The cradle carries the trunnions and is a nonrecoiling part. The recuperator piston rod and the recoil piston rods being attached
to
it.

MOUNTING THE CRADLE.

The recoil mechanism is of the hydropneumatic, long-recoil type, In the sleigh the length of recoil being constant for all elevations. are bored five longitudinal cylinders, the upper two being forging
bored about half the length of the sleigh and are closed at the front end by caps, forming air reservoirs. The left reservoir has an opening in which the pressure gage is fitted to test the pressure of air or
gas.

The lower

cylinders extend the full length of the sleigh, while the

two outer cylinders form the recoil and the middle the recuperator The recuperator cylinder is connected by passages to the cylinder. two air chambers, permitting the liquid from the recuperator to flow
into them.

hollow and are fixed rigidly to the In the hollow space travel the throttling rods, which move with the recoiling parts. These rods are so shaped that they give a throttling effect on the liquid which passes through annular openOn return to battery the throttling rods ings around the piston.
recoil piston rods are

The

cradle.

act as a buffer to prevent violent return into batten-.

309

310

311
air (or nitrogen gas) in the recuperator is maintained at a pressure of 568 pounds per square inch, which is sufficient to keep

The

Tanks of compressed the howitzer in battery at all elevations. are kept at hand to replenish that in the recuperator in nitrogen
case the pressure gets low.

The

and

recoil cylinders is a

mixture

of glycerine

liquid used in both recuperators and water. Suitable

pumps

are provided for filling these cylinders.

A firing handle is fitted on the left side of the cradle, which,

through

a system of shafts, operates the percussion hammer on the breech the firing handle being accessible at all elevations of the howitzer.

In case of emergency the piece may be fired by means of a lanyard. The elevating mechanism consists of elevating arcs, which tip the cradle, is operated by a handwheel on the left side of the carriage

MOUNTING THE TOP CARRIAGE.
through a system of gearing.
obtained.

A maximum

elevation of 60

can be

In connection with the elevating gear a quick-loading gear is provided, by means of which the howitzer can be quickly brought to the loading angle (9 15') and again elevated without the use of the slower method of using the elevating gear. handwheel on the

A

right side of the carriage is used to operate the quick loading gear. The top carriage is a structural steel, built-up unit. The top of the

forming the top carriage carry the trunnion bearings for the At the front of the carriage a pintle bearing is provided, which bears on the pintle of the platform, thus providing a means of
flasks

cradle.

rotating the top carriage and traversing the piece. pinion at the roar of the carriage meshing with a rack on the platform swings the

A

312
rear end of the carriage in traverse. center is thus obtained.

A

traverse of 10

each side of

on the top carriage is used for setting up and the unit. dismounting At the rear of the top carriage is attached a loading platform on which is mounted a loading crane for handling the shells. On the
loading platform tracks are provided for a rammer car which is used to transport a projectile from the loading crane to the breech and to ram it into the bore of the howitzer. This ramming of the projectile
is accomplished by means of a movable; chain on the rammer car which has suitable lugs for engaging the shell and is operated by cranks on the rammer car. The platform on which the top carriage rests is a structural-steel unit composed of a top and bottom plate secured by channels. The middle portion is open and has a trunk section to provide a space

A windlass mounted

for the howitzer to recoil at high angles of elevation.

The

traversing

METHOD OF LOWERING PLATFORM.
rack is secured to the rear end of the platform. Built-up steel floats are attached to the rear of the platform by swinging arms, which function to give stability to the mount at extreme angles of azimuth. Axle brackets and attachments for the false trail of the transport wagon are provided for use when traveling.
Accessories.

A

considerable

number

of tools

and accessories are

required for the erection, operation, and maintenance of the piece. The principal ones are as follows: Erecting frame, shot truck, sights, transport wheel tracks, track for shot truck, shell tongs, shot barrow,
air

pump,

liquid

pump, hydraulic
is

jacks,

wheel blocks and mats, axle-

lifting levers, etc.

composed of structural-steel beams. It is operated by hydraulic jacks and is used in assembling and dismounterecting frame

The

ing the piece.

When

It may also be used as a derrick for handling shells. used for this purpose, a trolley attachment with shell tongs is

provided.

313

314

315

The shot truck
a track which
is

is

laid

a four-wheeled vehicle with flanged wheels fitting from the magazine to the piece, and will carry

two of the
rails joined

projectiles.

The track
is

for this truck

is

600 millimeters

(23 1 inches) gauge.

It

supplied in built-up lengths of light steel

by

pressed-steel ties.
Weights, dimensions,

and

ballistics.

Weight Length

of howitzer
of

pounds.
inches.

.

10,

790

howitzer

.

399. 6

Right hand, 1 turn in 40 calibers at origin to 1 turn in 20 caliRifling bers at a point 24.369 inches from the muzzle.

Height to center of trunnions pounds. Weight of howitzer and transport wagon do Weight of cradle and transport wagon do Weight of top carriage and transport wagon do f Weight of platform and transport wagon do Weight of complete unit in firing position do Weight of erecting frame Sleigh (complete, filled with liquid and all pistons, packings, caps, etc.) -do do Cradle (complete, but without elevating arms) do Recuperator (steel forging only), completely machined do Elevating arms (including quick-loading gear) Top carriage (complete, with elevating and traversing gear, windlass,
.

AND WAGONS.
In order to transport the complete carriage there are provided four transport vehicles, namely, the howitzer transport wagon, top
carriage-transport wagon,

transport wagon. trail, rear axle, and wheels.

Each wagon

platform-transport wagon, and cradleconsists principally of a limber, false

HOWITZER TRANSPORT WAGON.
of two wheels, an axle, pole, and turning arc, all which are similar for each wagon. The pole is composed of two steel parts joined with a flexible spring coupling, consisting of a coil spring, plunger, and hinged joint, providing a movement of about 15 inches at the end of the pole to
of

The limber consists

CRADLE TRANSPORT WAGON.

between the limber and the be coupled. This spring coupling also vehicle may relieves the vehicles of any sudden shocks during transportation. Each limber is provided with a pintle over which fits the lunette ring of its false trail. Safety chains are attached to the pole to hold the false trail on the pintle in proper position.
for
to

make up

any which

difference in height
it

(318)

319

The turning
it

arc

is

attached to the axle and the false
pintle.

trail

bears on

as it rotates

around the

provided, one for each wagon. They are similar in most respects, especially the front end that has the lunette This lunette ring floats in the trail and is surrounded by ring.

Four

false trails are

coiled springs

which take up the shocks incidental to transportation.

TOP CARRIAGE TRANSPORT WAGON.

The body
which
it

is formed to suit the heights of the unit to attaches and has brace rods for stiffening. locking arrangement is provided to lock the units to the false trails and is

of the false trail

A

operated by means of a hand lever. The rear axle of the transport wagon

is

made

shaped to suit the unit which

it carries.

The

of a special forging axle for the howitzer-

Ij^V <PMj

^^mn

r?1i

PLATFORM TRANSPORT WAGON.

wagon is curved to suit the radius of the howitzer and has which lock the howitzer in place. pawls Band brakes are used and are alike for all four types of rear axles, but the brake-operating mechanism is different for the various transport wagons. The brakes on each vehicle are connected by a connecting lever shaft which is operated by a lever with ratchet and
transport

pawl.

Provision

is

made

for the setting of the brakes

by the operator

18322820

21

320
of the hauling tractor

by means

of a rope attached to the operating

lever

and extending

to the tractor.

When the complete carriage is set up for firing, the transport vehicles are close coupled by the false trail and form short units, having four wheels which can be drawn away. Brackets are provided
attached to each axle for the brace rods which are used
vehicles are unloaded
tired wheels.
Weights and dimensions.

when the

and close coupled. Both the limber and rear axles are equipped with standard rubber-

ANTI-AIRCRAFT ARTILLERY.
In considering the question of antiaircraft materiel it is to be rethe science of anti-aircraft gunnery has changed probto a greater extent than that of any other branch of the service. ably It was unheard of at the beginning of the war, and in consequence has grown from nothing at all to an important phase of operations. As a result, materiel is constantly changing and can not be said to have reached a definite basis even at this time. The materiel was greatly " affected also by the change from position warfare" to warfare of from a somewhat neglected factor to one motion; portability changing

membered that

paramount importance. In field artillery practice range problems are presented in connection with mortars, howitzers, and guns, but the results to be accomplished and the problems in connection with each of these weapons are quite
different.

of

The provided elevation

of the

guns of some calibers

is

small, while the muzzle velocity of some of the howitzers and all of the mortars is comparatively low; also the traverse of all three differ-

ent types of weapons is limited. The field target is usually stationary, maps being available for establishing its position, and ample time is available in which to figure its range. Observation of the point of

one shot serves as a guide in correcting the range for the next Frequently it is possible to choose atmospheric conditions under which the weapon would be employed, and assisting or opposing longitudinal windage, or driftage due to side windage, is calculated with the aid of wind gauges.
fall of

shot.

For anti-aircraft service the problem is entirely different. The single weapon must be able to cover the elevations of all three types of the field artillery weapons and preferably have a traverse of 360.
These wide variations in elevation introduce serious recoil problems, andT the difference in the traverse problem may be to some extent
illustrated

by

reference to the fact that the total traverse of the 75-

millimeter French, model 1897 Ml, field gun is only 6. Instead of a stationary target there may be presented one whose speed is one-sixth of the speed of the projectile itself and whose course can in no wise be forecast by road direction or terrain formation and whose position may be at any vertical or horizontal angle. The possible altitude and speed of airplanes increased from time to time, making useless the earlier and present basic data to be employed in the design of protective materiel. Under certain conditions of airplane approach the range must be calculated on the instant and there As the target is not stais no choice as to atmospheric conditions. corrections are difficult to estimate by observation. tionary, range
(322)

323
While gauges may indicate the direction and force of the wind at the which they are set, they furnish no indication of air currents existing at other altitudes through which it might be necessary
altitude at

With the flat trajectory of a for the anti-aircraft projectile to pass. fieldpiece at but a few degrees elevation, the density of atmosphere
through which the projectile must pass
is

largely uniform, while at

high angles of fire with anti-aircraft guns the projectile through atmospheres of different rarefactions, and hence different resistances to the passage of the projectile. These influences affect the
trajectory of the projectile, the rate of travel of the projectile, time element of the burning of the fuze.

and the

With

field artillery,

an impact

fuze,

shrapnel is employed with both a time fuze and and high-explosive shell with impact fuze only, but

324
anti-aircraft disrupting projectiles are fitted only with time fuzes, as otherwise a projectile which has missed its aerial mark would be apt to cause damage within friendly lines through impact explosion on reaching the ground.

As there is practically no position which is entirely free from the possibility of aircraft attack, and as there is no means of determining the direction from which such attack may come, ready mobility of
guns is most desirable, and as opportunity to reach the frequently only momentary, rapidity of sighting and of firing is essential. In the case of indirect fire from a camouflaged position, the gunner has not even had a view of the approaching plane, but
anti-aircraft

target

is

must lay

his gun on the basis of telephone data, or data otherwise transmitted from the battery commander's station. The anti-aircraft target may be a balloon either stationary or towed a dirigible, or an airplane, but is most frequently the latter.

simple, as

Location of the position of balloons or dirigibles is comparatively compared with airplane location, owing to the size of the For night target and the stationary position or low speed of motion.
searchlights or other illuminating means are required, and for fire or protective fire in thick weather, sound-locating devices

fire,

night

are employed.

The earlier fire from anti-aircraft artillery was directed solely from the burst; that is, by firing a shot, and judging of the direction of the next shot solely by observation of the nearness to which the burst of the first shot had approximated the position of the target. In the
meantime, however, the position of the target had changed. This system has given way to the use of an elaborate system of instruments for the determination of fire in accordance with certain established
principles.

In the attack upon aircraft the desired end
either

may

be accomplished

disabling of its occupants, in which latter case the destruction of the aircraft would follow. The methods adopted include destruction by incendiarism,
direct hits, by flying particles from exploding shell or shrapnel, and by shell shock. Methods of fire may involve explosive projectiles from a single gun, salvos or barrage fire from a number of guns, rapid firing from pom-poms (small caliber guns, firing explosive projectiles), or from machine guns firing small arm ammunition. Because of the important field played by aerial sound-detecting apparatus, searchlights, and telephony, including wireless, future

by the destruction

of the aircraft itself or

by the

by

progress in the design of anti-aircraft artillery will consider these With the perfection of airplane motors and their interconsubjects. nected functioning apparatus, the design of aircraft, and the art of
flying, other factors

upon which the design

of artillery

equipment

should likewise be based, enter into this problem.

325

3-INCH ANTI-AIRCRAFT
It is

GUN MATERIEL, MODEL 1918.

hardly possible to estimate how great will be the future importance of the perfection of the country's aerial defense from a strategic point of view. Aviation as an offensive arm will remain a
principal arm, and anti-aircraft artillery, as a defense branch, will play the part that coast artillery plays to the naval squadrons.
of gunnery, such one more complisubject, cated than any other artillery problem, and consequently one which Deessentially demands new methods and modes of measurement. however, has led to the design of the 3-inch auto-trailer velopment,

1917, mounted on a four-wheel trailer truck, having springs and solid rubber tired wheels. The gun and the mount remain fixed on the trailer, both in traveling and in battery positions. The muzzle velocity of the gun is 2,400 foot-seconds. Both shrapnel and high-explosive shells, each weighing about 15 pounds,

are employed.

At a maximum elevation

of 85

the

maximum

verti-

cal ordinate, limited by the time fuze, is 7,940 meters. At minimum elevation of 10 the projectile strikes the ground at approximately 6,100 meters. At 23 elevation the bursting vertical ordinate is

1,176 meters, meters.

and the horizontal ordinate approximately 7,025

The recoil mechanism is similar to that employed with the American 75 millimeter, model 1916, field gun, but with the use of a spearhead counter-recoil buffer. This recoil mechanism is of the hydrospring type and the variable adjustment of the stroke is governed by a rotating valve, the movement of which moves port holes behind
the edges of three lands permitting the passage of oil to the bypassing recesses. The anti-aircraft gun, together with the recoil mechanism, is held by the cradle and swings from 10 to 85 elevation in the trunnion bearings of the top carriages. A base plate rigidly bolted to the trailer chassis supports the top carriage on traversing rollers on which the top carriage rotates 360 in azimuth around a pintle on the base
plate.

The

trailer carriage is

lifting jacks

which,

when

equipped with outriggers. Stability and in firing position, rest on detachable floats
(326)

327

328
on the ground and support the entire weight of carriage and trailer. These outriggers and jacks are employed to stabilize this unit when in action and to prevent the mount from overturning when the gun is fired at low angles of elevation.

VIEW OF REAR OUTRIGGERS FOLDED; OUTSIDE END OF RIGHT OUTRIGGER BRACE READY TO BE PLACED IN RECEPTACLE; SCREW JACK WITH OUTRIGGERS FOLDED.

In traveling position the outriggers are folded up, the jack screws raised, the floats and spades being carried in another vehicle, with the exception of the stability jack floats which are attached to the jack screws. Traveling locks are provided to lock the gun at about

329

331
20 elevation to protect the elevating mechanism. In azimuth the carriage is locked lengthwise of the trailer to remove unnecessary strains from the traversing mechanism when the unit is traveling. Adjustable seats and foot rests for the gunners and platforms that
fold
is

up when traveling are fastened to the top carriage. This unit considered able to negotiate any roads suitable for field artillery. Weight of complete unit is approximately 14,000 pounds. Fixed ammunition is used with these guns, consisting of timeshell,

fuzed high-explosive, illuminating shell, tracer All the shell and shrapnel are issued fuzed.

The gun, of which there are two models, 1918 and 1918MI, is built up of nickel-steel forgings and consists of a tube, a jacket, and a breech ring, the latter being screwed to the rear end of the jacket forming a housing for the breech mechanism. Lugs are provided at the top and bottom of the breech ring to which are secured, respecThe 19 18MI tively, the recoil cylinder and counter-recoil spring rods. model differs from the 1918 model only in the jacket which is 1.6 inches longer at the threaded part allowing a greater thickness of metal in rear of the jacket, thereby strengthening the gun around the chamber. The breech mechanism is practically the same as that used on the 75-millimeter field gun, model of 1916 (American) (see p. 73), being of the drop block type, semiautomatic, and operated by a handle on the right side of the breech which is pulled backwards and down to

open the breech.
Weights, dimensions,

and

ballistics

of gun.

Weight
Caliber

of

gun (including breech mechanism ).

pounds

.

.

1,

966
3

inches.

.

Total length of gun Length of bore

-do. ... 129. 69
:

do
cu. in
.

Volume
Length

of

chamber

:

.

120 200
95.

of rifled portion of bore of grooves

inches.
inches.

.

Number
Width Depth Width

87 24

of grooves
of grooves of lands

.

0.

2927
0. 0.

do
do. ...
.

03
10

ft. per sec. Muzzle velocity Twist, right hand increasing from one turn to 50 calibers at the origin to one turn in 25 calibers at a point 8.87 inches from the muzzle and uniform from

2,

400

that point to the muzzle.

332 The carnage comprises the top carriage and cradle. The top carriage consists of two side frames bolted to a bottom plate which in turn rests on a circular roller frame and rotates about a pintle on

VIEW OF RIGHT REAR OUTRIGGER WITH JACKSPADE AND FLOAT REMOVED AND BRACE DROPPED FROM SHACKLE AT INSIDE END; LEFT REAR OUTRIGGER IN POSITION, WITH FLOAT CONNECTION FOLDED.

The base plate is rigidly bolted to the trailer chassis with outriggers and stability and lifting jacks which equipped when in firing position, rest on detachable floats on the ground and
the base plate.

and

is

support the entire weight of the carriage

trailer.

The top

carriage

333
prevented from tipping or lifting from the traversing rollers by a front and rear clip which are fastened to the bottom plate and which engage an annular flange on the base plate.
is

The recoil mechanism is of the variable recoil hydro-spring type and operates the same as that of the 75-millimeter field gun, model of 1916. The only noticeable difference between the two is that a

334
spear buffer is used instead of a valve in the buffer rod head as is used in the 75-millimeter gun. The length of recoil varies from 16 inches at 85 elevation to 40 inches at 10 elevation.

An
cradle

elevating arc having teeth is secured to the lower side of the and meshes with a Hindley worm which is driven through

bevel and spur gears

by a handwheel
is

located on the right side of the
left side of

the top a worm, a worm carriage. gears, wheel, and a friction clutch, rotates a pinion which in turn meshes with an annular rack bolted to the base plate. The pinion when rotated causes the top carriage to revolve about its pintle on the

top carriage. The traversing mechanism

attached to the

The handwheel, through bevel

traversing rollers. Four seats are attached to the top carriage, two on either side, which are used by the personnel who operate the sights and elevating

and traversing mechanisms. Platforms are bolted to both sides at the rear of the top carriage for the personnel who load and fire the piece. The platforms may be folded up and the seats swung to one side for traveling. When traveling, the gun is locked at an elevation of about 20 and lengthwise of the trailer by upper and lower traveling locks for the purpose of taking up any strains or shocks which might come on the elevating or traversing mechanisms.
Weights and dimensions of Carriage.

or ammunition) Weight of trailer with carriage, gun, and ammunition chest only Weight under front wheels (fully equipped) Weight under rear wheels (fully equipped) Weight of one round of ammunition (complete)

pounds do do do do
degrees

.

.

4,

13,
7, 7,

26. 8
. .

Maximum angle of elevation Minimum angle of elevation
Traverse of carriage Maximum length of recoil Minimum length of recoil Number of rounds in ammunition chest Number of rounds in spare ammunition chest Height from ground to center of trunnions

do do
inches
do.
. .

360 40
10
14 16

. . .

inches

.

.

85

Height from ground to top of gun Maximum width of carriage

(in traveling position)

Maximum length Maximum length

of carriage of carriage

(drawbar up) (drawbar down)

do do do
do.
.

119
77

230 243

335

CO

18322820

22

336
carriage is mounted consists of two between which are secured the cross members, bracing and making up the complete chassis. Between the front and rear wheels the frame is so depressed that the base plate of the carriage is on the same plane as the hubs of the wheels, thus bringing the center of gravity of the carriage lower and lessening the possiThe space at the front of the trailer formed bility of overturning. the side frames and cross members is provided with a bottom by

The

trailer

upon which the

parallel side frames,

FRONT VIEW.
plate, a top plate

and hinged cover, and
is

is

utilized as a tool box.

The

similar to the front, except that a support is for the ammunition chest. The chest which carriqs 16 provided rounds of ammunition also serves as a seat for the operators of the

rear section

foot rest is fastened to the rear tool box cover. The carriage. chassis is supported on the axles, both front and rear by semielliptical springs.

A

The

trailer is

towed and steered by a drawbar equipped with a

lunette and fastened to the front axle in such a

manner that the

(338)

339
the path of the truck or tractor by may also be steered by the rear wheels when the rear wheel lock is released and the steering bar is inserted. A pintle is provided on the rear end of the trailer to accomtrailer will actually follow in
it is

which

drawn.

The

trailer

modate any

which may be attached thereto. equipped with a brake of the internal expanding type operating within drums attached to the rear wheels and applied and released by a lever on the right side of the trailer by one of the
vehicles
is

This vehicle

personnel seated on the ammunition chest.
Weights and dimensions of Trailer.

Wheelbase

inches.

.

156
60
48.

Width

of track of

Length

Width

of

frame over all frame over all

do do do
pounds.
inches.
. .

Weight

of chassis

3,

Size of tires

200 125 800 37
6

Width

of tires

.do

Height from ground to center line of drawbar Height from ground to top of frame, empty Diameter of brake drum

sight issued for anti-aircraft carriages, model of 1918, consists two units, one being mounted on the right trunnion of the cradle and the other on a bracket attached to the left side of the carriage, the two units being connected by a coupling shaft. The elements on the right side are the range and elevation corrector and those on the left side are the angle of site and deflection corrector. An open sight is
of

The

attached to the sight proper for rapid location of the target. All necessary points for night firing are illuminated by the electrical equipment. A 6-volt system is used, the current being supplied by dry batteries, storage battery, or by a manually operated generator. Small lamps of one or two candlepower shielded by reflectors,
are used to illuminate the necessary scales

and cross

hairs.

3-INCH ANTI-AIRCRAFT
The
ators

GUN MOUNT, MODEL OF 1917.

from carrying out

principle use of anti-aircraft artillery is mainly to hinder avitheir missions. The destruction of airplanes,

with the means actually at its disposal, is still a question of luck. Experience has taught aviators to defend themselves against fire by
continual changes in direction.

a direct hit by the projectile which is fired from the considered that the possibility of such hit is too remote. The artillery practice is, therefore, to so direct the projectile that it will explode at a more or less predetermined position and cause

damage through
it is

gun, as

damage either by the fragmentation of the projectile, which covers a very much larger volume than the intact projectile, or through the concussion caused by the exploding projectile and whose effects would also be felt through a considerable sphere. No one t}-pe of anti-aircraft gun carriage or mount can possibly
satisfy all conditions of

modern warfare.
(340)

It

is,

however, possible to

341

342

343
design a standard gun and top carriage having a wide range of action and by means of interchangeability enablingJthis mount to be used on either a truck mount, a two or four wheel trailer, a caterpillar
tread trailer, or as a semifixed mount, as each of these types of vehicles has its own sphere of action. However, the problem of seacoast

defense and for the defense of depots,
3-inch anti-aircraft

etc., led to

the design of the

gun mount, model

of 1917.

The

3-inch anti-aircraft

stant recoil, designed to be

mount is of the barbette type, with conmounted on a solid concrete base about

VIEW SHOWING RIGHT SIDE OF MOUNT.

30 inches thick and IS feet in diameter.
to

The gun mount is designed mount the 3-inch anti-aircraft gun, model 1917, 1917, MI, or 1917 Mil, commonly known as the 1 5-pound er gun. The gun has a 12-inch recoil and a muzzle velocity of 2,600 footBoth high explosive shell and shrapnel may be employed, the weight of the projectile being 15 pounds, and of the complete round of fixed ammunition being 28.38 pounds.
seconds.

The gun is mounted on a cradle of the sleeve type, which also serves as a housing for the spring and recoil systems. The cradle is

344
suspended by the trunnions from the top of the pivot yoke. The pivot yoke is bolted to the racer, which rests and revolves on 30 rollers on the roller path of the base plate. The base plate is held in position in the emplacement by 16 anchor bolts set in the concrete.

The

field of fire is

360,

to 90

elevation.

Removable stops

are provided, however, to limit the elevation of 85, due to possible injury to the personnel when the piece is fired at a higher angle. Fixed ammunition is used in these guns, consisting of a time-fuzed

high-explosive shell, illuminating shell, tracer shell, and shrapnel. Each round consists of the cartridge case with its primer and powder

The model of 1917 gun is built up of alloy steii, consisting of tube, and locking hoop. The jacket envelops the rear portion of the tube and forms the recess or seat for the breech mechanism. A r ecoil lug projects from the upper surface of the jacket near its extreme end and affords a point of attachment for the piston rod of the recoil cylinder. A lug also projects from the under surface, to which are attached the counterrecoil spring rods. The locking hoop is forced on the tube and forward end of the jacket, securing the latter against any rearward movement of the tube under firing
jacket,
stresses.

The model
model
is

of 1917

MI gun

is

similar in general construction to the

of 1917 gun, except that instead of the breech ring being The breech end of jacket integral with jacket, it is a separate piece.

threaded to receive the breech ring, which

is

screwed and shrunk
is

on the jacket and held by a lock screw.

The locking hoop

omitted.

345

346

347

The model

of 1917

Mil

is

similar in general construction to the

model of 1917 MI, except in the method of securing the latch plate On the models of 1917 and 1917 Ml, the latch plate to the gun. to gun by screws, while on the 1917 Ml the latch plate is is secured
secured to gun by means of a lug. The breech recess is rectangular in shape. Two extractor trunnion seats, one in each side, are cut to the proper radius for the extractor Two holes are drilled from the rear face of the to rotate and slide.
side, to accommodate a spring and plunger which the hub of the extractor, keeping it in place and also press against aids the extractor in ejecting the cartridge case. The breech mechanism consists of the following parts: Breech

of the drop-block type and is rectangular in run lengthwise on the block, giving a wedging grooves shape. effect against the end of the cartridge case when the block is closed, and when opened insuring a clearance between the cartridge case and the block thus eliminating any chance of the cartridge case jamming. A venthole permits the escape of gas from a ruptured primer. Two extractor grooves, one on each side of the block, are cut parallel to the guide grooves and curve to a certain cam development which permits the proper action of the extractors. At the top

The breechblock

is

Two

of the block a radius
projectile.

is

The

toe of each extractor

cut to permit of clearance when inserting the is cut to a radius which will

just slide along the body of the cartridge the run of the cartridge case.

when

in place

and engage

mechanism belongs to that type known as the continuous-pull mechanism; that is, no cocking of the firing pin is required other than a pull on the lanyard or trigger shaft. This arrangement permits of repetition of the blow from the firing pin in

The

firing

case of a misfire, as often as desired without the opening of the

mechanism.
Weights, mount, etc.

mount only Weight Weight of gun and mount
of

pounds.

.

12,

do. ... do. ...
do. ...

15,
7,

Weight of gun and cradle Weight of cradle and recoil systems Weight of yoke with elevating and traversing mechanisms Weight of traversing rack, friction band, roller cage, and base plate Weight of sight and supports

4,
5,

do. ... do. ...

3,

175 280 105 000 100 000
75

do. ...

The mount is emplaced in a concrete emplacement, in which 16 anchor bolts are set, and depressions provided for 8 leveling screw
thrust plates. connections are

A

niche for an outlet box, through which electrical made to the main base, or for a storage battery when

348
generated current is not available, is constructed in the concrete to meet the requirements of the mount. This emplacement is constructed by the Engineer Corps, which also furnishes and installs the necessary outlet or storage battery and furnishes the plug box portable lamp, cable, and plug. The principal parts of the mount are the base plate; racer; pivot

upper surface machined to form the lower Sixteen holes, equally spaced around the circumference

of the flange, are provided to receive the foundation bolts which retain the base plate in its proper position in the emplacement.

A

cylindrical projection in the center forms on its interior the housing for the 360 electrical contact, and on its exterior receives the trav-

ersing rack. The racer
bolted.

is

The" under surface

a circular steel plate, upon which the pivot yoke is is machined to form the upper roller

path, and the upper surface to fit the yoke. The racer rests on the rollers and rotates freely about the hub on the traversing rack. Two front and rear, are bolted to the under side of the racer, and clips,

engage with a lug on the base plate to prevent the racer from leaving the rollers, and overturning the mount, when the gun is fired. The pivot yoke is a steel casting, consisting of two vertical side frames joined in front by a transom. At the top of each frame is a trunnion bearing and trunnion cap lined with bronze bushings. Tapped holes are provided in the left frame for the depression and elevation stop. The distance ring is a circular bronze ring provided with spaces and bearings for the traversing rollers. The traversing rollers, 30 in number, are interposed between the roller paths of the base plate and racer, bearing the weight of the mount. The rollers,
roller paths, traversing rack, and pinion are protected from the entrance of dust, sand or grit, by dust guards. The oil grooves on the

circumference of the distance ring serve to distribute oil from the holes in the flange forming the base of the yoke to the axles of the rollers. friction band, resting on the base plate, is made to grip

A

the traversing rack. To adjust this band, which allows slipping of the traversing rack to protect the teeth of the traversing pinion from too heavy a stress, a cover in the base of the yoke is removed,
giving access to the parts beneath. Motion of the mount in azimuth
is obtained by a traversing pinion and shaft, the pinion meshing with the teeth of the traversing rack. Power is transmitted from the traversing handwheel to the traversing

349

350

351

worm, thence to the mount through a set of gears and a clutch mounted in the traversing gear case. Two speeds of traverse are possible upon throwing the clutch in by means of a handle, so that
high or low speed gears are connected to the upper traversing shaft. The elevating mechanism consists of an elevating rack keyed to the underside of the cradle, having on its face teeth which mesh with the elevating worm. The rack is of sufficient length to provide for ele-

bored and bushed to receive the gun. Front and rear In addition liners are provided through which the gun slides in recoil. forms the housing for the recoil and counterrecoil systems. the cradle The interior of the cradle has a cored recess to suit the firing mechis

vations from The cradle

to

90.

anism.
is

The recoil cylinder Recoil mechanism is of the hydro-spring type. screwed from the front into a seat provided in the top of the cradle. The piston rod is attached to the gun lug at one end and provided at the other end with a piston, slightly smaller than the bore of the Three longitudinal throttling grooves are cut in the cylinder. interior surface of the recoil cylinder, each groove subtending an arc of 30. With the cylinder in assembled position one groove is located at the bottom. The recoil cylinder has a capacity of 6J
pints of hydroline
oil.

cylindrical holes bored in the cradle form the housing for the counterrecoil springs. Spring rods are attached at one end to the gun lug and at the other end to the spring-rod piston. When the spring compressor is first assembled it is secured against rotation by a

Two

retaining screw. The counterrecoil plunger, designed to check the recoiling parts as they return to battery, passes through the front end of the recoil cylinder and enters the recess in the forward end of the piston rod.
recoils to the rear about 12 inches in the the recoil piston and spring rods, thereby compressing the counterrecoil springs. portion of the energy of recoil is taken up by the resistance the liquid offers to being forced through the variable slots formed by the throttling grooves and the

When

the

gun

is fired it it

cradle, carrying

with

A

constant clearances between the piston head and the interior surface of the cylindrical bore, the remainder of the energy being absorbed by the springs. The width of the grooves is uniform, but their depth is proportioned so that the areas of the orifices, varying with the position of the piston during recoil, will be such as to give, with the aid of the counterrecoil springs, a constant resistance throughout the length of recoil. The pressure in the cylinder is therefore a uniformly
decreasing one. The counterrecoil buffer
is

tapered so that the escape of

oil

during

counterrecoil, through the varying diametrical clearances 18322820 23

between

352
the plunger and the hole in the piston, will offer such resistance as motion of the gun during its return to battery position after firing. The firing mechanism consists of a firing handle whose shaft passes

will control the

through the center of the right trunnion and carries on its inner end a lever which operates the firing shaft. Previous to the firing the gunner pulls the firing handle which compresses the cocking spring solid and moves the lever on the breech to the tripping position; the gunner will know when the mechanism has reached this

To

position by feeling the increased pressure exerted by the firing spring. fire the gun, the gunner pulls the firing handle, compressing the

firing spring,

of the firing handle moment of firing.

thus tripping the firing pin. The two-stage movement is intended to permit a shorter movement at the

circuit has a 360 contact mounted in the base Direct-current mains of either 110 or 220 volts are connected with an outlet box located in the concrete emplacement. Two circuits are led from the 360 contact, one leading to the

The illuminating

plate.

plug box for use as a portable lamp of line voltage, and the other circuit leads to the switch box; from here it is led to the rheostat from which two branch feeders are taken to the two receptacle boxes and bolted to the yoke. A circuit is taken from the right receptacle box with a spliced branch feeder to a candelabra receptacle for the

Another circuit is run reticule lamp and deflection pointer lamp. from the left receptacle box with two spliced branch feeders to a
candelabra receptacle for the elevation pointer, range disk pointer, and elevation correction lamps. These lamps are supported by lamp brackets fastened to the trunnion and sight mechanism. The rheostat used cuts down the voltage and makes the use of
low-voltage lamps and batteries practicable in case the line voltage
fails

through accident.

rheostat

cable leading from the 360 contact with the plug, switch, and is of the twin conductor, leaded, and armored type. The two branch feeders leading from the rheostat to the receptacle boxes and thence to the lamp brackets are of the portable conductor type.

The

The various cables are fastened straps and twisted hooks.

to the

mount by means

of cable

This instrument Sight for antiaircraft mount, model of 1917. used to direct the elevating and traversing of includes all parts mount so that the gun may be pointed properly in elevation and
consist of a sight proper (telescope), the sight mount, range disk, correction scale, and pointer. For any visible target the data necessary to properly lay the gun consists of fusedirection.

The parts

setter range, travel in elevation arbitrary correction.

and

deflection,

and the required

353

The

target

is

brought into the

field of

view by turning the azimuth
to the sight a

and the angle-of-site knobs, imparting azimuth and elevation, respectively.

movement

in

is provided whereby the sight proper may be set in elevaany desired angle, whence the gun by means of the elevating mechanism is also elevated to the same angle (corrections being zero). An azimuth scale is also provided between the fixed and rotating parts of the carriage so that the gun by means of the traversing mechanism may be set at any desired angle in azimuth.

A scale

tion at

75-MILLIMETER ANTI-AIRCRAFT TRUCK MOUNT.
(MODEL OF
To appreciate the
sider that one
is

1917.)

difficulty of anti-aircraft fire it suffices to con-

firing practically at a bird whose velocity is about 50 meters per second, i. e., one-sixth the average velocity of the The projectile itself in the case of the 75 -millimeter field gun. principal result hoped for by the anti-aircraft artillery fire is to prevent airplanes from accomplishing their mission by obliging them to fly

to

at increasing altitudes, to continually change their direction, and also prevent their crossing certain regions. At the present time the anti-aircraft artillery aims to keep airplanes

beyond the
to fly

limit of their range. Observation airplanes are obliged out of range, reconnoitering airplanes continually increase the

TRUCK

IN

TRAVELING POSITION (RIGHT SIDE VIEW).

height at which they cross the lines, and battle planes must also fly very high, except when they wish to attack trenches or batteries with machine guns. Raids of this kind are almost exclusively carried on at night. The result is that three kinds of fire have

become particularly important:
Fire against airplanes at a great range and a great height. Fire against very speedy airplanes attacking positions. Fire at night against bombarding airplanes. The need of an anti-aircraft weapon to meet the above requirements led to the design of the 75-millimeter anti-aircraft truck mount.

This development involved the use of an American model 1916 field gun, equipped with a hydro-spring recoil mechanism having throttling
(354)

55

356

1

357
valves cut in the cylinders. This gun and recoiling mechanism is secured on an offset swivel gun mount, suitably mounted on a 2J-ton

White gasoline-driven

truck,

Model TBC, designed

to receive the

base plate of the top carriage.

The gun (see p. 72) is carried on a cradle which rocks in elevation about the trunnions of the top carriage, and, by means of the elevating mechanism, a range of elevation from 31 to 82 is obtainable. The piece has a recoil of 33 inches on its cradle and is provided with a
and uses and shrapnel shells, the former weighing 14.7 pounds high-explosive and the latter 14.3 pounds, employing a 20-second (maximum) time
fuze with
each.
recoil cylinder, counter-recoil springs, and buffer. The piece has a muzzle velocity of 1,830 feet per second,

With a maximum

vertical

elevation of 82

a

vertical bursting ordinate of 5,980 meters is obtained, and with the minimum elevation of 31 a vertical bursting ordinate of 1,750

VIEW SHOWING TRUCK MOUNT IN ACTION.

meters
limited

is

obtained.

In both cases the bursting ordina^es were
is

by the time fuze. The gun with the breech

located directly behind the driver's

seat, but as the length of recoil is fixed, the firing position is limited to such horizontal position of the mount as would permit of the gun

recoil clearing the sides or rear of the truck chassis. heavy base plate is secured to the rear end of the chassis, and the top carriage swings in azimuth about a central pintle bolt on

A

rollers.

By means

of

the

traversing

mechanism,

the carriage,

gun and its corresponding mechanism, can be traversed through 240, which is the field of fire. The chassis is equipped with firing and stability jacks to relieve the rear springs and truck of all With the jacks properly placed and leveled, the firing strains. vehicle is supported on a rigid horizontal platform formed by the
carrying the
firing jacks

and the base

plate.

When

in action the stability equip-

ment .functions to prevent the mount from overturning when the gun is fired at low angles of elevation.

358
Weights, dimensions,

and

ballistics.

Caliber Total length of gun Length of the rifled portion of the bore Length in calibers

mechanisms, cradle, elevating and traversing mechanism, angle of sight mechanism, firing jacks, stability jacks, and rails. The base plate is a rectangular steel casting secured to the truck
the top carriage
is

support for the top carriage. The traverse of by lugs provided on the top of the clip surface. The clip prevents the traversing rollers from leaving their path due to the shock caused by action of recoil or counterrecoil. Four lugs radiating from the pintle bearing serve as points of attachment for the firing jacks and rail tie rods. At the forward end of the base plate are two lugs, one on either side, which project out at right angles to the truck chassis, serving as points of attachment for the
chassis, and, serves as a

limited

The firing strains produced during action are jacks. transmitted through these lugs and jacks, thus eliminating all unnecessary strains from the rear springs and wheels of the truck. The top carriage is a steel casting, comprising a base and two vertical side frames designed to mount the cradle to permit sufficient clearance for the recoiling parts at high angles of fire. pintle bolt projecting
stability

A

from the base plate through the case of the top carriage forms an axis about which the carriage is rotated in azimuth upon four rollers resting on the roller path of the base plate. Between the two side frames is housed the angle of sight mechanism. The traverse of the carriage

359
is

limited to 240 by means of a traversing stop plunger, which engages the lugs on the clip surface. When preparing for travel the stop plunger can be raised to clear the limit stop, thus permitting the proper position of carriage when en route. Four seats (two on each side) riveted to swinging arms, for the use of the cannoneers during action, are secured to the top carriage. Recoil mechanism. The recoil mechanism is of the hydro-spring Three longituditype, with recoil cylinder mounted above the gun.

nal ribs, or throttling bars, of uniform width but varying height, are formed on the inside of the cylinder and engage with corresponding

grooves in the piston head. The clearance between the bars and grooves determines the amount of oil which may pass from the back to the front of the piston head, thereby regulating the amount of recoil. The piston rod is a hollow steel tube and is fitted with a bronze head. The rear end of the piston rod is bored out to accommodate the counterrecoil buffer, which fits into the bore with a small clearance. This clearance depends on the taper of the buffer, as the hole in the piston rod is of constant diameter. In each spring cylinder, three coils of inner and outer counterrecoil springs are assembled over the spring rod. The inner and outer springs are wound in opposite directions to prevent nesting, and each pair of inner springs is separated from the next pair by a bronze
separator.
recoil cylinder

the gun moves back on its slides carrying with it the and counterrecoil springs. The piston rod is secured to a nonrecoiling part of the carriage, thus when the recoil cylinder
fired,

When

moves

the other.

to the rear, the oil in it must pass from one side of the piston to The energy of recoil of the gun is absorbed by the resist-

oil offers to being forced through small openings past the piston, also by the compression of the counterrecoil springs. The energy stored up by the springs returns the gun to battery position.

ance which the

The return movement

is eased and regulated by the counterrecoil which prevents any undue shock to the recoiling parts by buffer, offering resistance due to the fluid in the hole of the piston rod being

forced out as the buffer gradually enters the hole. The cradle comprises the counterrecoil spring cylinders with their component attached parts. The spring cylinders are below the gun
in the form of two cylinders joined at the center. Above the cylinders are the bronze lined gun ways or slides. The trunnions are secured to the cylinders, and the elevating arc is bolted to lugs on the bottom. Riveted to the right side of the cradle is the elevation

and

is journaled upon the trunnions. Bearings are provided in the bottom of the rocker for the elevating mechanism and a rack is cut on the exterior of its yoke for the angle

stop and the depression stop. The rocker, a U-shaped forging,

of sight

worm.

360
The traveling lock is located under the rear end of the spring cylinder. This device functions to lock the cradle at an angle of approximately 32 in elevation when preparing for travel, thus the elevating angle of

GUN MOUNT SHOWING GUN AT MAXIMUM ELEVATION.
site

and traversing mechanisms are relieved

of all

unnecessary vibra-

tions
is

the front end of the base plate hinged a lock bar and brace, which engage a lug provided on the rear the vehicle
is

when

en route.

At

361
In order to bring this lug in proper position to the cradle must be traversed to its traveling posireceive the lock bar, tion, that is, to bring the axis of the gun into a vertical plane with the

end

of the cradle.

center line of the truck chassis.

The elevating mechanism consists of an elevating worm, an elevating arc or rack, and a train of miter gears mounted on the right side of the The shaft on which the elevating handwheel is mounted rocker. extends through the side frame of the top carriage. The worm is operated through gears and a shaft by means of a handwheel, and rotates the cradle about the trunnions. Any movement imparted to the worm by the handwheel will cause the cradle One turn of the handto move with relation to the top carriage. wheel will cause the gun to be elevated or depressed approximately

TRUCK
1.7.

IN

TRAVELING POSITION (LEFT SIDE VIEW).
arc permits a change of elevation

The elevating
to 82

from 31 mini-

mum

maximum.

The traversing mechanism located on the left side of the top carriage* consists mainly of a traversing handwheel and shaft, worm, worm wheel, clutch, bevel pinion, traversing pinion, and rack. The worm
engages the worm wheel and can be either engaged with or disengaged from the shaft by means of a clutch operated by a foot lever. If the clutch be disengaged, the worm and worm wheel are released from the gear train, and the top carriage may be traversed about the The traversing pinion engages the traversing pintle bolt by hand. rack which is secured to the base plate. One turn of the handwheel will cause the gun to be traversed approximately 2.
shaft,

The angle of site mechanism consists of a handwheel, handwheel and angle of site worm. The angle of site worm is secured to the top carriage and engages in a rack cut in the face of the yoke of the rocker. To one end of the shaft which extends out to the right

362
side of the top carriage fixed a miter gear.
is

secured the handwheel and to the other end

is

The angle of site worm is a one-piece forging comprising a worm, a shaft, and a miter gear of the same size as that on the bracket at an angle of 90 to the handwheel shaft and with the miter gears at, the ends in mesh. One turn of the handwheel will cause the rocker
and the cradle to be elevated The rocker allows a correction
elevation.

or depressed approximately 25 mils. of 124 mils depression and 200 mils

Firing and stability jacks. The principal parts of the firing jacks are the jack body, jack screw, foot, and spade. There are two firing the bodies being hinged at the rear corners of the base plate jacks, as shown on page 363. At the end of the jack screw the foot, or float,

secured by a ball joint which enables the jack to be seated on The foot is provided with a sharp-pointed spade, which is driven into the ground. A tie rod is used between the two jacks to keep the jack bodies from spreading out when the load is put on the screws. The firing jacks act as rigid supports for the base
is

inclined surfaces.

plate at the rear corners, and relieve the truck chassis of firing strains. The stability jacks are essentially the same in construction as the
firing jacks, but heavier. ing of the truck when the

Their function
is'fired at

is

to prevent the overturn-

low angles of elevation, and gun also to take the firing strains. The stability jacks are hinged to the base plate, one on each side and each is supported by a strut hinged

in a lug secured to the truck chassis.

The

stability jack floats are

provided with spades.
the carriage is in the traveling position, the firing jacks and The spades are stability jacks are folded up and secured by chains. removed and placed in receptacles provided on the chassis. The stability jack struts are unpinned from the forward lugs, removed

When

and carried in holders on the base plate. The tie rods are folded with the jacks and chained in position. Two stability rails and tie rods are provided with each mount, one being straight and the other having an offset. They are crossed under the rear axle of the truck, the rear ends being located so that the firing jack floats set in the spaces between the angles of each rail. The middle angles at the front ends of the stability rails are attached to the stability rail tie rods, which in turn are connected to the adapters on the lugs, directly opposite the firing jack lugs, on the base plate. When the vehicle is to be emplaced, both of the truck wedges are placed on the ground with the channel side up, and the front wheels of the truck are run up the channels between the flanges. The purpose of these wedges is to raise the front end of the truck so that the mount will be level when the rear end is jacked up. Two steel blocks are provided for blocking the front wheels when they are run up on the truck wedges.

363
Rear axle slings. When traveling, the slings hang loosely under the truck, one on either side of the transmission. The front ends of the slings are looped around through holes in the base plate and clamped in place permanently. Two steel rods are inserted in the rear loops of the slings and placed across the rear end of the chassis when the mount is emplaced, and two pieces of pipe are inserted in the front loops of the slings and placed across the ribs on the front end of the base plate. The purpose of these slings is to keep the

FIRING AND STABILITY JACKS. rear springs compressed

and the rear wheels

off

the ground

when

the

jacked up. The electrical equipment consists of five lamps receiving current from a storage battery, suitable wiring, and switching arrangements. Two three-cell, 6 to 8 volt batteries are provided, one for reserve, each of 120-ampere-hour capacity, and are carried in a metal container which is bolted to the chassis of the truck. One battery,

mount

is

when

fully, charged and in good condition, will furnish energy for about 24 hours' continuous service for all lamps.

364
is permanent and the connecting wires are protected by armor wherever mechanical injury is likely. Should it be necessary to remove the top carriage, the lead from the battery which runs through the pintle bolt may be disconnected above the top of the bolt by unwrapping the insulation and opening the con-

All wiring

steel

necting plug there provided. The lamps are specially designed to withstand the shock of firing and are rated at 2 candlepower. One lamp is provided for illuminating each of the following parts
:

Deflection correction pointer.
Keticule.

Elevation pointer.

Range

disk pointer.

Elevation correction pointer.

TRUCK MOUNT

IN

BATTERY POSITION.

switch is provided in the main battery lead which controls the lamps, and the lamps should be disconnected by means of this switch when not in use.
all

A snap
The

cludes

sight for this antiaircraft vehicle is an all parts used to direct the elevating

mount

so that the

gun may

instrument which inand traversing of the be pointed properly in elevation and

parts consist of a sight proper (telescope), the sight mount, range disk, correction scale and pointer. For any visible target, the data necessary to properly lay the gun consist of fuze setter range, travel in elevation and deflection, and any desired

azimuth.

The

arbitrary correction.

The object is brought into the field of view by turning the azimuth and the angle of site knobs imparting thereby to the sight a movement in azimuth and elevation respectively. The object is followed
by continuing the movement of these knobs. Detailed description of the model 1917 anti-aircraft sight may be found in separate
pamphlet covering
fire-control instruments.

TRENCH WARFARE MATERIEL.
The trenches constitute the most advanced position of a combat army and the equipment and supplies placed at the disposal of those occupying them are generally classified under the broad heading of

Trench warfare materiel." The trench forms protection against horizontal firing and permits of secret massing of troops for surprise attacks, and it is the constant aim of the Air Service, with its photographic equipment and telegraphic communications, to reduce this element of surprise. Concealment of the general outline from airplane observation is impossible, but details may be concealed, for an observer in an airplane can not see whether a trench is occupied unless the airplane flies
dangerously low.

"

The trenches

are carried

up

to within 200 yards or less of the ene-

my's front line and are the scene of constant watchfulness to prevent enemy advance and of constant attempts to reduce the enemy personnel, lower his morale, capture prisoners for the purpose of obtaining
information, and to advance the position of our own lines. The field artillery is located from 1 to 5 miles or more behind the
front line, in order to protect it from sudden rushes by the enemy, while the infantry, machine gun, and trench mortar personnel occupy

the trenches interlaced through the intervening terrain to afford this protection and also to place the personnel of the army in a position to come into contact with the enemy without being obliged to pass

over a wide intervening stretch of terrain under enemy fire. The operation of all branches of the service are interrelated, and nothing is haphazard or independent of the comprehensive plan, save during the heat of action or in the event of units becoming isolated, and such movements are temporary only in their independence, as their effects are consolidated with the complete plan so soon as opportunity permits. The air service, field artillery, the signal service and the tanks are all coordinated through headquarters with the service of the trenches and communication is maintained

through an elaborate system of telephone and telegraph wires, pyrotechinic flashlights, flare, or other visual signals. The trench system includes a front-line trench of

broken

line for-

mation, whose individual straight lines are from 9 feet to 18 feet in length. An enemy entering this trench can sweep only the length of
(365)

366

TRENCH WARFARE.

367
the straight line, and must fight around a barrier for the balance of the trench. This trench is connected by communication trenches to a supervision trench located to the rear, and thence by other trenches, possibly several miles further back, into friendly territory.

The communication trenches are curved, elbowed or zigzagged and have T or L connections, island pockets, tunnels, bombing pits,
strong points, keeps, shelters, dugouts, or other provisions as the conditions may demand. Traps are arranged for the confusion of an enemy entering the trench, positions are arranged for dropping barbed wire, knives, or frames quickly into position to retard the advance of the enemy troops who have gained the trench. Machine gun and mortar em-

placements are built where needed and bomb-proof dugouts provided for rest quarters, storage and forward dressing stations for the treatment of wounded. The narrower a trench is the better the cover which it affords. Communicating trenches are made of sufficient width to permit of

ARRANGEMENT OF TRENCHES.
the carrying of stretchers, and thus allow for the evacuating of the

wounded during daylight. The wider trench submits it to greater effect from enemy artillery fire, but if trenches are not wide enough
for stretchers, losses result through the detention of casualties in the trenches until darkness permits of their removal to dressing stations.

The wider trench

also permits a

more rapid movement

of

supplies between the front line and rear areas, and thus reduces the time during which men and supplies are detained under

men and

concentrated fire, and hence reduces the casualties and destruction from this cause. Gas is a constant menace in the trenches, as it is heavier than air, and its effects vary with the nature of the gas employed. Flame or liquid fire is employed both with a view to inflicting injury to the enemy and lowering his morale. The presence of water is always taken into consideration, for the trench is open to water resulting from rainfall. Provisions are made for footing and drainage, advantage being taken of natural slope where possible.
183252820
24

368
Trench warfare has shown the necessity for hurling large charges of high explosives for comparatively short ranges. This necessity has led to the development of the trench mortar, a type of weapon that is a short smooth bore of simple construction. They are muzzle loaders and use as their projectile a thin- walled shell, known as a
trench-mortar bomb. In trench warfare the role of trench artillery is to harass the enemy by engaging living targets where opportunity offers, to attack and destroy enemy defensive works and obstacles within range limits, and to prevent the construction of new works. The trench mortar is essentially a trench artillery weapon of limited range which will render very efficient service when properly emplaced, skillfully handled and served. The trench mortars are divided into three classes, light, medium,

and heavy calibers. The light trench mortar
is

is

very mobile.

Its effect against material

particularly effective against massed troops, or troops driven into the open, due to its rapidity of fire. These mortars are used to form a barrage behind the hostile line to prevent
is

inconsiderable, but

reserves and

ammunition being brought up. Owing to their high limited only by the difficulty of ammunition supply, they mobility, are especially fitted to accompany the infantry as it advances, and
are used to attack machine-gun shelters

and other points which have checked the forward movement of the infantry. temporarily The medium trench mortar, with its range of approximately 1,200 meters, is very effective against wire entanglements, machine-gun shelters, strong points, trenches, and other similar objectives not
too strongly protected. The heavy trench mortar
is designed for the attack of heavily protected shelters and dugouts, trenches, machine-gun shelters, and

strong points. It is seldom used against wire entanglements because of the large crater formed by the explosion. In most types of trench mortars the propelling charge is carried at the base of the bomb and is ignited by striking a pin at the breech The bomb is dropped into the muzzle and slides down of the piece. by its own weight until the firing pin ignites the charge.

The types now issued

to the service are

:

3-inch Stokes trench mortar, Mark 6-inch trench mortar, Mark I.

I.

The
pages.

characteristics of each type will

be discussed on the following

3-INCH STOKES

TRENCH MORTAR (MARK

I).

The 3-inch Stokes trench mortar is of British origin, and proved a very useful and excellent weapon owing to its simplicity, light weight, and the principle of auto-ignition. Its principle has practically been

copied by both the French and our 'armies and applied to other mortars.

The mortar essentially consists of the following components: A smoothbore barrel, a bipod, and base, the complete unit weighing
108 pounds.

The

barrel

is

a seamless
(369)

drawn

steel tube,

lapped to

370
size

To

the breech end

and necked down at one end and called the breech or base end. is fitted a base cap, within which is secured a
protruding into the barrel.

firing pin

The

barrel

is

supported near

the muzzle end, by a steel bipod fitted with elevating and traversing screws. The recoil of the mortar is taken up by a base plate against

which the base cap of the barrel

rests.

FRONT VIEW OF TRENCH MORTAR.
elevating stand is made of tubular steel, consisting of two attached to a center trunnion by means of a compass joint; these legs legs are held apart by a cross stay which is arranged to spring just past the dead center in such a manner as to hold the two legs rigidly

The

The trunnion standard is fitted with a pair of bevel gears operated by a handle, by means of which the elevating screw can be rapidly raised or lowered. The upper end of the elevating screw
apart.
is fitted

with a yoke to support the transversing screw shaft, which,

371
together with a traversing handle and a dog clutch, forms a bolt and is held in position by a locking pin. traversing screw carried the traversing screw shaft and driven by the dog clutch forms the by means of traversing the mortar by engaging a nut fixed to the barrel.

A

The

the locking pin

barrel can be quickly disconnected from the mounting by lifting and withdrawing the traversing bolt. The barrel may

then be lifted out of position. The base plate has three depressions. The shape of the base cap permits the lower end of the barrel to rest in any of these depressions, and by shifting the barrel from one to another a change of 6

REAR VIEW OF TRENCH MORTAR.
in direction of line of fire can be
position.

made on

either side of the center

In firing position the base plate is embedded in the ground at about a 45 angle. The lower end of the barrel is placed in the indentation in the base plate which gives the barrel the direction nearest to that desired, the upper end of the barrel being supported by the legs of the bipod. Minor adjustment for direction is secured by means of the traversing screw. The barrel is then given the elevation corresponding to the desired range by operating the elevating screw. The range quadrant (or clinometer) being set for the desired range, indicates when the barrels has the proper elevation.
,

372

The

shell or

bomb used with

this

mortar

is

a cylinder loaded with

high explosive, fitted at its head with a detonating fuze. The weight of the shell is approximately 11 J pounds. The propelling charge
consists of 12-gauge shotgun shell, which fits in a cartridge container at the rear end of the shell. To secure additional range, 1 to 3 rings

The of ballistite can be placed around the cartridge container. secured with cartridge alone varies from 150 yards at 75 range
to 300 yards at

reaches a

With cartridge and three rings, the range of 750 yards at 40 elevation. The firing operation is as follows The shell with propelling charge in position (the cartridge inserted in the cartridge container and the
40.

maximum

:

rings around the container) is dropped into the muzzle of the mortar, cartridge end first, and slides down the barrel. The primer of the cartridge is fired on impact with the firing pin. Ignition of the ballistite rings is obtained from the flash of the cartridge through ports in the cartridge container. The shell, carrying the cartridge case with
it, is

projected from the barrel and the mortar

is

ready for another

shell.

The extreme rate of firing under average conditions is about 25 rounds per minute, but 10 rounds per minute is considered the average effective rate. The crater formed by the shell has a depth of about 2 feet and a diameter of about 4 feet.
Weights of mortar.
Pounds.

Barrel, ring, clamp, traversing screw, and base cap

Bipod (mounting complete) Base plate__

43 37 28

6-INCH
This mortar
is

TRENCH MORTAR (MARK

I).

an American adaptation of the British 6-inch

Newton trench mortar. It is operated by dropping the shell down the While the prinbarrel of the gun and thus igniting the propellent. ciple of firing is the same as in the 3-inch Stokes mortar, the mounting is somewhat different, in that no bipod is employed; the breech
end of the barrel resting on a cupped base plate and being supported an overhanging position therefrom by three guy rods. This weapon is a most effective agent against machine-gun nests, barbedwire entanglements, fortifications, etc., but is seldom used against
in

personnel.

This mortar consists of the following essential components
Barrel with clinometer.

:

The platform, The sub-base.

base, guys,

and

fittings.

The barrel is of one piece, muzzle loading, having a smooth bore. The breech is closed and rests in a hemispherical socket supported upon a stationary platform to which the barrel is stayed by three adjustable guys. The elevation, which varies from a maximum of 75 to a minimum of 40, and lateral deviation is made by altering the length of the guys, which are adjustable by means of handwheels. These are determined by the setting of the clinometer attached adjustments The range can be varied by changing either the elevato the barrel. tion of the gun or the weight of the propelling charge. The setting up of this mortar is a more elaborate proceeding than the setting up of the 3-inch Stokes mortar. The cast steel base is bolted to a hardwood platform, which is mounted on a sub-base made up of timbers and a rectangular iron frame bolted together. The subbase may in some cases be dispensed with, as shown on page 373.

The

barrel

is

furnished internally at the breech end with an axial

firing pin or anvil and externally with a guide stud and a misfire plug. Should the ignition cartridge fail to function when the shell is dropped down the barrel, the misfire plug permits of the intro-

duction of a small powder charge with fuze for the ignition of the propelling charge. Graduations are engraved on the barrel on the right and left of a zero line and are used for traverse setting of the
clinometer.
(373)

374

375

The base is a steel casting having a machined hemispherical socket on the upper side to receive the rounded end of the barrel and provided with a guide groove which engages the guide stud on the barrel
hardwood platform. Elevating and upper side of the platform, while traversing guys of the guys are hooked into devices on the barrel when the free ends the latter is mounted on the base. Special hooks provide a method
to the

when in position. The base is bolted

are anchored to the

LEFT SIDE VIEW OF 6-INCH TRENCH MORTAR.

of fastening the guys during transportation. Four wire-rope handles are provided as a means for carrying the platform.

quadrant graduated with an elevation which oscillates about a center on the quadrant. The bubble carrier is provided with a pair of cross bubbles. The clinometer is attached to the mortar barrel by steel bands and a clamping screw. In laying of the piece, an arrow on the quadrant is set to coincide with the desired traverse and the indicator on the bubble carrier is also set coincident with the desired elevation. The guys are then
consists of a
scale

The clinometer

and straddled by

a bubble carrier

376
adjusted so that both bubbles are exactly level, the barrel of the gun
in the desired direction.

ejector consists of a metal head to fit the bore and a tube end of which is a handle. When the gase ejector is pushed down the barrel the burned gases are forced up through the handle and out of the gun. When the gas ejector is removed cold air is sucked through the handle and into the gun. The head is threaded to receive a wire brush or a sponge head whenever it is desirable to clean
at one

The gas

or sponge out the bore.

METHOD OF LOADING TRENCH MORTAR.

The projectile is a cast iron fragmentation shell with vanes, weighing approximately 42 pounds unloaded, and containing a bursting charge of approximately 11 pounds of high explosive. The projectiles are fitted with delay and nondelay fuzes. The propelling charge
silk

consists of sporting ballistite contained in

With these two sizes of bags number of combinations can be obtained and the range can be varied according to these combinations. The maximum charge is
bags of
1

and 2 ounces capacity.

a

377
9 ounces and the minimum 3 ounces. The bags are held in place between the vanes of the shell by a propelling bag holder. The charge is ignited by an ignition cartridge made from a standard rifle cartridge which is fired when it strikes the firing pin as the shell reaches the bottom of the barrel.

PROSPECTUS.
The trend of design for field artillery now proposed and under way shows several digressions from the present practice. Motor transportation promises to almost completely revolutionize A motor-drawn carriage is not so limited in weight artillery design. as the horse-drawn type, thus permitting heavier and more powerful weapons. At the same time the carriage must be designed to withstand the more severe usage of motor traction. A further development along the line of motor transportation is the The performance self-propelled caterpillar mount for field artillery. of the experimental mounts of this type has been very satisfactory, and no doubt manufacture in quantity will be ordered in the near
mounted with a suitable top carriage directly on the caterpillar, and thus forms a self-contained unit capable of rapid and easy maneuvering. This type of mounting permits of carrying various calibers of guns and howitzers, and has the further
future.

The

piece

is

advantage of permitting all around traverse by maneuvering the vehicle under its own power. They are also able to negotiate rough and difficult terrain more readily than any other type of vehicle yet
developed.
self-propelled caterpillar, Mark II, 8 units of which have been recently issued to the service, is a road vehicle of the track-laying type; that is, the power is transmitted to the ground through a

The

flexible, endless

track composed of steel shoes, instead of directly through the drive wheels as in the usual type of truck construction. This caterpillar has been designed and constructed to mount the

155 mm. gun, and be able to withstand its firing stresses. Although not primarily a hauling or towing type of machine, it is provided with a rear pintle for towing an ammunition trailer or similar vehicle. On each side at the front of the main frame draw hooks are provided for

towing the mount when necessary. The various units composing the vehicle are assembled on the main frame which is a rigidly reinforced steel casting. The main frame is supported on the track by truck roller frames on which it rests through the medium of an equalizing mechanism and spring buffers.

The power unit

of this vehicle

is

mounted

longitudinally at the

forward end beneath the muzzle end of the gun, consisting of a U FT" six-cylinder internal combustion engine with its fuel, Sterling
carburetion, ignition, lubrication, and cooling systems.
(378)

379
is transmitted to the drive sprockets, which master clutch the following power system. drive the track through of power between the engine and main transcontrols the application mission unit containing selective gears by which the speed and direcFrom the transmission unit the power tion of travel are controlled.

The power developed

A

is

transmitted to two propeller shafts through the steering clutches and reducing planetaries. These propeller shafts transmit the power from the intermediate transmission to the final drive gears on the
drive sprockets.

PLAN VIEW OF SELF-PROPELLED CATERPILLAR,

MARK

II.

The driving mechanism is so designed that the forward travel of the vehicle is the pointing 'direction of the gun. The combination of
selective

reverse.

and planetary gears provides four speeds forward and two The direction and speed of travel are under the direct control of a single operator, seated where he is able to obtain full view ahead and may readily gain access to engine in case of emergency. The planetary brake, the master clutch, and the gear shift are operated by hand levers. The planetary brake and steering clutch on the same propeller shaft are operated by the same lever. Having a separate lever for each propeller shaft the steering clutches and planetaries can be operated separately or simultaneously, as desired, and in this way the vehicle is steered.

380

When both steering levers are in the forward position, the steering clutches are engaged, and power is transmitted to both tracks at the direct speed. By placing the right steering lever in the central or
neutral position, the right steering clutch is disengaged and power is transmitted to the left track only and the vehicle can be made to turn

sharply to the right

by applying

the right steering clutch brake.

Placing the right steering clutch lever in the rear position sets the planetary brake and reduces the speed of the right so that the In a similar manner the vehicle vehicle turns slowly to the right. can be turned to the left by the use of the left steering lever. Applying both planetaries at the same time furnishes a reduced uniform

speed to both tracks and a low gear ratio for a hard

pull.

With both

381
steering levers in neutral, or with the master clutch disengaged, both brakes may be set simultaneously by the use of the hand lever located

between the two foot brake pedals.
direct drive
is

The speed and

direction of the

by the selective transmission gear-shift lever, which can only be operated when the master clutch is disengaged, thereby breaking the power between the engine and the transmission.
controlled

deck plates directly over the transmission case, planetary and steering clutches are removable to provide ready access brakes, for repairs and adjustments. Doors are provided in the sides of the armor plate engine hood for the same purpose. The equalizer arrangement is pivoted at the front end of the main frame and operates so that one track, when passing over a log or
steel

The

382
obstruction, forces th.3 track on the opposite side down into firm, bearing with the ground, thus preventing the caterpillar tipping sideways, or the front end riding up and running down with a jar when the center of gravity passes over the obstruction. The forward end of the caterpillar is covered with steel plates forming a protecting nose when forcing its way through brush, trees, and other field

obstructions.
rear deck plates under the gun breech are hinged so that they be folded back out of the way to enable the gun crew to load and may handle the gun from the ground.

The

A

traverse of the
to the left
is

gun

and 5

relative to the caterpillar of 5 to the right provided, which is sufficient for corrections and

accurate pointing. Any necessary traverse beyond this limit is obtained by traversing the caterpillar vehicle under its own power by the use of the steering levers. Under ordinary ground conditions an
all

around traverse can be obtained

in this

way.

The

to 35

range

elevation of the standard wheeled carriage is retained in this mount. structural steel deck, with necessary guard railing is secured to

A

side plates of

main frame, and extending over the

entire length of the

tracks, thereby preventing accidents to the personnel during travelbig, and may be conveniently used for mounting of the sight, tool

and spare part

chests, etc.,

when deemed

necessary.

This self-propelled caterpillar type unit has successfully demonstrated its advantages, for, due to its mobility, it may readily be transported from place to place under unfavorable ground and weather conditions and is able to open fire immediately upon its The advantage of this type of machine having arrival in a position. mounted directly on a vehicle with caterpillar treads for artillery
military purposes lies in its ability, due to very low unit ground pressure, to negotiate soft and uneven surfaces, imposible to the usual type of power vehicle, except under the most extreme difficulties.

Anti-aircraft guns are receiving careful attention with the view
of further
pieces.

development
are

They

caterpillars, or

of easily maneuvered and quickly handled mounted on self-propelled vehicles, as trucks or on some easily drawn vehicle such as an auto trailer.

They must of course be designed for all around and high angle fire. Used as they are against swiftly moving aircraft, special guns of high velocity and sights specially adapted to this work must be
considered.

Several changes are apparent in the trend of design for
pieces of the wheeled type.

new

field-

The desirability of wider traverse and higher angles of elevation has led to the development of the split trail carriage for both guns

and howitzers.

Many

of the

newer guns permit

of as high elevation

as that of the howitzers.

Another development
for the

same
is

veloped

is that of interchangeable guns and howitzers For example, one type of carriage being decarriage. that for mounting a 75 millimeter gun or a 105 millimeter

howitzer.

The hydro-spring type
recoil

of recoil

entirely superseded in the latest designs

mechanism seems to be almost by the hydropneumatic

mechanism.

in latest practice is to relieve the carriage from road shocks as much as possible by the use of spring suspension and rubber- tired wheels. The desirability of small light fieldpieces which can be taken to the front by the infantry has led to the infantry accompanying gun and howitzer. Some of the latest experimental guns of this type are 2. 24-inch pieces so light that they are easily moved by man power. In general, it will be seen from the above that future artillery will more nearly approach the ideal, to the degree that the principles of high power and swift transportation are incorporated in the design.

The tendency

18322820

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demand may be renewed
expiration of loan period.

if

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is

made

before

DEC 18 1924

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